[Manual Backport 2.x][MD] Support SigV4 as a new auth type of datasource

[ananzh]

• [Multiple DataSource] Add support for SigV4 authentication

Backport Issue

#3058

Check List

• All tests pass
  • yarn test:jest
  • yarn test:jest_integration
  • yarn test:ftr
• New functionality includes testing.
• New functionality has been documented.
• Update CHANGELOG.md
• Commits are signed per the DCO using --signoff

[codecov-commenter]

Codecov Report

Merging #3458 (c4bf76a) into 2.x (e484a7a) will decrease coverage by 0.06%.
The diff coverage is 40.41%.

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@@            Coverage Diff             @@
##              2.x    #3458      +/-   ##
==========================================
- Coverage   66.48%   66.42%   -0.06%     
==========================================
  Files        3203     3205       +2     
  Lines       61397    61551     +154     
  Branches     9453     9492      +39     
==========================================
+ Hits        40821    40888      +67     
- Misses      18315    18396      +81     
- Partials     2261     2267       +6     

Flag	Coverage Δ
Linux	66.37% <40.41%> (-0.12%)	⬇️
Windows	66.37% <40.41%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...omponents/validation/datasource_form_validation.ts	75.86% <0.00%> (-24.14%)	⬇️
src/plugins/data_source_management/public/types.ts	100.00% <ø> (ø)
...s_credential_modal/update_aws_credential_modal.tsx	5.26% <5.26%> (ø)
...gins/data_source/server/client/configure_client.ts	46.66% <35.71%> (-19.38%)	⬇️
...rce/components/edit_form/edit_data_source_form.tsx	70.74% <38.35%> (-20.03%)	⬇️
...components/create_form/create_data_source_form.tsx	75.26% <41.66%> (-21.71%)	⬇️
...c/plugins/data_source/server/client/client_pool.ts	46.66% <45.00%> (-12.16%)	⬇️
...ta_source/server/legacy/configure_legacy_client.ts	59.61% <50.00%> (-11.22%)	⬇️
...ata_source/server/client/configure_client_utils.ts	64.70% <64.70%> (ø)
.../plugins/data_source/server/data_source_service.ts	71.42% <100.00%> (ø)
... and 8 more

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[zhongnansu]

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