Adjust filter plugin validation requirements to comply with Moodle 4.5

[kabalin]

This patch is addressing filter plugin validation compliance with 4.5 raised at #321. Filter API have been updated to use the standard Moodle Class Autoloading infrastructure (https://moodledev.io/docs/4.5/devupdate#filter-plugins), this introduced requirement for backward compatibility in addition to new filter class location.

Possible Moodle version compatibility options for plugins now become:

• 4.4 and below → expect file filter.php containing class filter_[pluginname].
• 4.5 → expect file classes/text_filter.php containing class text_filter.
• 4.5 and below → expect file classes/text_filter.php containing class text_filter and file filter.php containing class_alias.

Possible Moodle versions test scenarios matrix:

• Moodle 4.5, plugin compatibility 4.5 → pass
• Moodle 4.5, plugin compatibility 4.4 and below → fail
• Moodle 4.4, plugin compatibility 4.4 and below → pass
• Moodle 4.4, plugin compatibility 4.5 and below → pass
• Moodle 4.4, plugin compatibility 4.5 → fail

The patch implements validation logic listed above and introduces 2 new methods:

• getRequiredFunctionCalls in plugin type specific Requirements class to validate that file contains function call.
• FileTokens::notFoundHint can be used to give some context for validation error to improve developer experience.

Currently this tool does not support the determine version compatibility declared in version.php ($plugin->supported), for this simple scenario I use file existence check as indicator of backward compatibility implemented in plugin, in future the tool would possibly benefit from using information from $plugin->supported property.

Changeset has been tested locally with https://github.com/gjbarnard/moodle-filter_synhi plugin:

4.5, filter_synhi main:

 RUN  Validating filter_synhi
> Found required file: version.php
> Found required file: lang/en/filter_synhi.php
> Found required file: classes/text_filter.php
! Skipping validation of missing or optional file: db/upgrade.php
> In classes/text_filter.php, found class filter_synhi\text_filter
> In lang/en/filter_synhi.php, found language filtername
! Skipping validation of missing or optional file: db/install.xml
> In filter.php, found function call class_alias

4.5, filter_synhi main, filter.php deleted:

 RUN  Validating filter_synhi
> Found required file: version.php
> Found required file: lang/en/filter_synhi.php
> Found required file: classes/text_filter.php
! Skipping validation of missing or optional file: db/upgrade.php
> In classes/text_filter.php, found class filter_synhi\text_filter
> In lang/en/filter_synhi.php, found language filtername
! Skipping validation of missing or optional file: db/install.xml
! Skipping validation of missing or optional file: filter.php

4.5, filter_synhi V402.1.0:

 RUN  Validating filter_synhi
> Found required file: version.php
> Found required file: lang/en/filter_synhi.php
X Failed to find required file: classes/text_filter.php
! Skipping validation of missing or optional file: db/upgrade.php
! Skipping validation of missing or optional file: classes/text_filter.php
> In lang/en/filter_synhi.php, found language filtername
! Skipping validation of missing or optional file: db/install.xml
X In filter.php, failed to find function call class_alias
X Hint: https://moodledev.io/docs/4.5/devupdate#filter-plugins

4.4, filter_synhi V402.1.0:

 RUN  Validating filter_synhi
> Found required file: version.php
> Found required file: lang/en/filter_synhi.php
> Found required file: filter.php
! Skipping validation of missing or optional file: db/upgrade.php
> In filter.php, found class filter_synhi
> In lang/en/filter_synhi.php, found language filtername
! Skipping validation of missing or optional file: db/install.xml

4.4, filter_synhi main:

 RUN  Validating filter_synhi
> Found required file: version.php
> Found required file: lang/en/filter_synhi.php
> Found required file: filter.php
! Skipping validation of missing or optional file: db/upgrade.php
> In classes/text_filter.php, found class filter_synhi\text_filter
> In lang/en/filter_synhi.php, found language filtername
! Skipping validation of missing or optional file: db/install.xml
> In filter.php, found function call class_alias

4.4, filter_synhi main, filter.php deleted:

 RUN  Validating filter_synhi
> Found required file: version.php
> Found required file: lang/en/filter_synhi.php
X Failed to find required file: filter.php
! Skipping validation of missing or optional file: db/upgrade.php
> In classes/text_filter.php, found class filter_synhi\text_filter
> In lang/en/filter_synhi.php, found language filtername
! Skipping validation of missing or optional file: db/install.xml
! Skipping validation of missing or optional file: filter.php

[codecov]

Codecov Report

Attention: Patch coverage is 87.80488% with 5 lines in your changes missing coverage. Please review.

Project coverage is 88.34%. Comparing base (cd11318) to head (2b36993).

Files with missing lines	Patch %	Lines
src/PluginValidate/Finder/FunctionCallFinder.php	71.42%	2 Missing ⚠️
...uginValidate/Requirements/AbstractRequirements.php	0.00%	2 Missing ⚠️
src/PluginValidate/PluginValidate.php	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #326      +/-   ##
============================================
- Coverage     88.37%   88.34%   -0.03%     
- Complexity      738      757      +19     
============================================
  Files            76       77       +1     
  Lines          2296     2333      +37     
============================================
+ Hits           2029     2061      +32     
- Misses          267      272       +5     

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