feat: add data.load_balancer_type(s) data sources

[jooola]

Closes #945

[codecov]

Codecov Report

Attention: Patch coverage is 81.69014% with 26 lines in your changes missing coverage. Please review.

Project coverage is 69.88%. Comparing base (ac90449) to head (77912bd).

Files with missing lines	Patch %	Lines
internal/loadbalancertype/data_source.go	81.42%	17 Missing and 9 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #991      +/-   ##
==========================================
+ Coverage   69.67%   69.88%   +0.20%     
==========================================
  Files          64       65       +1     
  Lines        8010     8152     +142     
==========================================
+ Hits         5581     5697     +116     
- Misses       1727     1744      +17     
- Partials      702      711       +9     

Flag	Coverage Δ
e2e	69.88% <81.69%> (+0.20%)	⬆️
unit	34.21% <38.02%> (+0.06%)	⬆️

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[jooola]

This data source is almost finished, it is missing the following:

• the hcloud-go library does not provide the deprecated string field for the load balancer type https://docs.hetzner.cloud/#load-balancer-types-get-a-load-balancer-type, and I am not sure if we want to wait for the backend to implement the new deprecation object before we at it here.
• the documentation is written, but I am not sure if I missed anything.
• I am not sure what the -x suffix is used for in the docs sidebar sidebar_current template?