[Backport 2.x] Add support for dynamic application configurations

[opensearch-trigger-bot]

Backport 2c8d9d3 from #5855.

[codecov]

Codecov Report

Attention: Patch coverage is 85.57692% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 67.12%. Comparing base (bd04745) to head (1fcc362).

Files	Patch %	Lines
.../plugins/application_config/server/routes/index.ts	76.47%	8 Missing ⚠️
src/plugins/application_config/server/plugin.ts	78.94%	3 Missing and 1 partial ⚠️
.../plugins/application_config/server/string_utils.ts	77.77%	1 Missing and 1 partial ⚠️
...lication_config/server/opensearch_config_client.ts	97.61%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              2.x    #6003      +/-   ##
==========================================
+ Coverage   67.08%   67.12%   +0.03%     
==========================================
  Files        3308     3312       +4     
  Lines       63731    63835     +104     
  Branches    10168    10176       +8     
==========================================
+ Hits        42757    42848      +91     
- Misses      18509    18520      +11     
- Partials     2465     2467       +2     

Flag	Coverage Δ
Linux_1	35.21% <ø> (ø)
Linux_2	55.12% <ø> (ø)
Linux_3	44.63% <85.57%> (+0.12%)	⬆️
Linux_4	35.33% <ø> (ø)
Windows_1	35.23% <ø> (ø)
Windows_2	55.09% <ø> (ø)
Windows_3	44.64% <85.57%> (+0.13%)	⬆️
Windows_4	35.33% <ø> (ø)

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[tianleh]

Please help backport.

@kavilla @BionIT @bandinib-amzn

[tianleh]

cc @seraphjiang