feat: refactor nodejs region loader

[AllanZhengYP]

Description of changes:
Use @aws-sdk/node-config-provider package to load region in Nodejs. This change eliminates @aws-sdk/region-provider package. The purpose of this change is to consolidate all the server-side configuration loading, from config files, environment variables, and default valiues, to a single package.

The last commit is code generation. You can review the previous commits only for actual changes.

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[codecov-commenter]

Codecov Report

Merging #1437 into master will increase coverage by 0.59%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1437      +/-   ##
==========================================
+ Coverage   79.08%   79.67%   +0.59%     
==========================================
  Files         287      299      +12     
  Lines       11155    11391     +236     
  Branches     2360     2431      +71     
==========================================
+ Hits         8822     9076     +254     
+ Misses       2333     2315      -18     

Impacted Files	Coverage Δ
protocol_tests/aws-ec2/runtimeConfig.ts	100.00% <0.00%> (ø)
protocol_tests/aws-json/runtimeConfig.ts	100.00% <0.00%> (ø)
packages/util-create-request/src/index.ts	100.00% <0.00%> (ø)
protocol_tests/aws-query/runtimeConfig.ts	100.00% <0.00%> (ø)
protocol_tests/aws-ec2/protocols/Aws_ec2.ts	66.94% <0.00%> (ø)
protocol_tests/aws-restxml/runtimeConfig.ts	100.00% <0.00%> (ø)
protocol_tests/aws-restjson/runtimeConfig.ts	100.00% <0.00%> (ø)
packages/middleware-signing/src/middleware.ts	91.66% <0.00%> (ø)
protocol_tests/aws-query/protocols/Aws_query.ts	66.72% <0.00%> (ø)
...rotocol_tests/aws-restxml/protocols/Aws_restXml.ts	66.25% <0.00%> (ø)
... and 36 more

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