feat(platform-instance): a simple client-only change to support platf…

[swaroopjagadish]

…orm instances

Most dataset sources get a new config param:
platform_instance: <platform_instance_id>

Sources that create lineage-edges TO and FROM datasets in other platforms get a config mapping param:

platform_instance_map:
<platform_name>: <platform_instance_id>

Dataset urns look like:
urn:li:dataset:(urn:li:dataPlatform:<dataPlatform>),<platform_instance_id>.<name>,PROD when this is present.
urn:li:dataset:(urn:li:dataPlatform:<dataPlatform>),<name>,PROD when not present.

Adds a migrate command to help migrate old entities into the new id format.

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)

[github-actions]

Unit Test Results (build & test)

  66 files  ±0    66 suites  ±0   12m 49s ⏱️ - 1m 39s
581 tests ±0  522 ✔️ ±0  59 💤 ±0  0 ❌ ±0 

Results for commit 7a05984. ± Comparison against base commit 282851e.

[github-actions]

Unit Test Results (metadata ingestion)

       5 files  ±0         5 suites  ±0   36m 30s ⏱️ - 2m 58s
   275 tests +1     274 ✔️ +  1    0 💤 ±0  1 ❌ ±0 
1 266 runs  +7  1 235 ✔️ +11  30 💤  - 4  1 ❌ ±0 

For more details on these failures, see this check.

Results for commit 7a05984. ± Comparison against base commit 282851e.

[shirshanka]

LGTM!