feat(ingest): aws - support extra args to role config

[hsheth2]

• Adds support for external_id and other options in assume_role
• Makes it possible to use assume_role in conjunction with the other credential configs.
• Improves docs for all AWS config options.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[github-actions]

Unit Test Results (metadata ingestion)

    5 files    5 suites   41m 1s ⏱️
  52 tests 49 ✔️ 3 💤 0 ❌
103 runs  98 ✔️ 5 💤 0 ❌

Results for commit 8fca0c8.

[github-actions]

Unit Test Results (build & test)

562 tests  ±0   562 ✔️ ±0   12m 54s ⏱️ -52s
139 suites ±0       0 💤 ±0 
139 files   ±0       0 ❌ ±0 

Results for commit 8fca0c8. ± Comparison against base commit 63ef9c0.

[shirshanka]

LGTM