feat: add retry-config-provider

[trivikr]

Issue #, if available:
Internal issue at JS-1813

Description of changes:

adds retry-config-provider to read values from environment or config file:

	Env Var	Config File
maxAttemptsProvider	AWS_MAX_ATTEMPTS	max_attempts
retryModeProvider	AWS_RETRY_MODE	retry_mode

Similar to region-provider but with following differences:

• the defaultProvider passes the values to fromEnv and fromSharedConfigFiles as there are two methods to export
• fromSharedConfigFiles doesn't read for values from credentials file.
• doesn't export fromEnv and fromSharedConfigFiles as they're not required by external code.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #1282 into master will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1282      +/-   ##
==========================================
+ Coverage   73.04%   73.14%   +0.09%     
==========================================
  Files         287      290       +3     
  Lines       12730    12774      +44     
  Branches     2922     2933      +11     
==========================================
+ Hits         9299     9343      +44     
  Misses       3431     3431              

Impacted Files	Coverage Δ
packages/middleware-retry/src/defaultStrategy.ts	100.00% <100.00%> (ø)
packages/region-provider/src/defaultProvider.ts	100.00% <100.00%> (ø)
packages/region-provider/src/fromEnv.ts	100.00% <100.00%> (ø)
...kages/region-provider/src/fromSharedConfigFiles.ts	100.00% <100.00%> (ø)
...kages/retry-config-provider/src/defaultProvider.ts	100.00% <100.00%> (ø)
packages/retry-config-provider/src/fromEnv.ts	100.00% <100.00%> (ø)
...retry-config-provider/src/fromSharedConfigFiles.ts	100.00% <100.00%> (ø)

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[alexforsyth]

Can you verify that its a bug that the tests impact packages/middleware-retry/src/defaultStrategy.ts, and that the unit tests do not actually impact it?

[alexforsyth]

LGTM after minor feedback

[github-actions]

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