Shared Tree: Snapshot compatibility testing APIs

[TommyBrosman]

This change introduces a number of APIs for encoding schemas as snapshots and testing them for compatibility.

Description

The following alpha APIs have been added:

• checkCompatibility
• importCompatibilitySchemaSnapshot
• exportCompatibilitySchemaSnapshot

See the changeset for details on how to use them in tests.

Reviewer Guidance

• I would like feedback on the documentation. The intended audience is application developers authoring schema compatibility tests.
• I'm looking for suggestions on how to make the API unit tests more concise.

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  250224 links
    1778 destination URLs
    2015 URLs ignored
       0 warnings
       0 errors