enable importing CLI-managed subscription link extension

[AniTumany]

WHY are these changes introduced?

The current implementation only supports the legacy subscription_link extension type, but we need to also support the newer subscription_link_extension type.

WHAT is this pull request doing?

Adds support for the subscription_link_extension type in the import-extensions command by:

1. Adding subscription_link_extension to the list of extension types that can be imported as Subscription Link Extensions
2. Updating tests to include both the legacy and new subscription link extension types

How to test your changes?

1. Run the import-extensions command with an app that has a subscription_link_extension type
2. Verify that the extension is properly imported and the TOML file is created correctly

Measuring impact

How do we know this change was effective? Please choose one:

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix
• Existing analytics will cater for this addition
• PR includes analytics changes to measure impact

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes

[AniTumany]

• enable importing CLI-managed subscription link extension #5585 👈 (View in Graphite)
• main

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[github-actions]

We detected some changes at packages/*/src and there are no updates in the .changeset.
If the changes are user-facing, run "pnpm changeset add" to track your changes and include them in the next release CHANGELOG.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	76.62% (+0.02% 🔼)	9411/12282
🟡	Branches	71.8% (+0.03% 🔼)	4612/6423
🟡	Functions	76.38%	2444/3200
🟡	Lines	77.13% (+0.02% 🔼)	8895/11532

Test suite run success

2169 tests passing in 950 suites.

Report generated by 🧪jest coverage report action from 87512f9