Added the RFS HLD to the repo

[chelma]

Description

• Added the RFS high level design to the repo
• Added the diagrams in .svg format

Issues Resolved

• https://opensearch.atlassian.net/browse/MIGRATIONS-1720

Testing

• N/A

Check List

• New functionality includes testing
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented
• Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.80%. Comparing base (6692086) to head (6be1cd2).
Report is 16 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #649      +/-   ##
============================================
+ Coverage     75.63%   75.80%   +0.17%     
- Complexity     1541     1548       +7     
============================================
  Files           168      168              
  Lines          6455     6455              
  Branches        575      575              
============================================
+ Hits           4882     4893      +11     
+ Misses         1191     1183       -8     
+ Partials        382      379       -3     

Flag	Coverage Δ
unittests	75.80% <ø> (+0.17%)	⬆️

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