feat(ingest): add Python libs for Urns

[tc350981]

In the data model we define Urn as String which make it hard to manipulate. This PR creates python lib for Urn, DatasetUrn, DataPlatformUrn classes which is meant to help interact with Urn easier.

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 (metadata ingestion)

       5 files         5 suites   44m 15s ⏱️
   345 tests    345 ✔️   0 💤 0 ❌
1 572 runs  1 534 ✔️ 38 💤 0 ❌

Results for commit d3bf51c.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Results (build & test)

  70 files  ±0    70 suites  ±0   11m 11s ⏱️ -51s
611 tests +2  552 ✔️ +2  59 💤 ±0  0 ❌ ±0 

Results for commit d3bf51c. ± Comparison against base commit c89a1f2.

♻️ This comment has been updated with latest results.

[shirshanka]

This is great work and will make working with Urns much nicer. Thanks!
Have a few suggestions for you.

Also, how do you think we should transition from the make_x_urn pattern in mce_builder.py, since all connectors use that pathway today.

[tc350981]

This is great work and will make working with Urns much nicer. Thanks! Have a few suggestions for you.

Also, how do you think we should transition from the make_x_urn pattern in mce_builder.py, since all connectors use that pathway today.

maybe we could do it in phases, like:

1. change the implementation of make_x_urn to use x Urn class
2. Use Urn classes in new code
3. Soft deprecate the make_x_urn util function

[shirshanka]

LGTM!