Use locked major versions of GitHub actions

[Andarist]

1. locked versions, mostly to the latest @v3
2. moved shared setup to a composite action
3. upgraded Changesets action to v1
4. using yarn --frozen-lockfile consistently for all install jobs
5. bumped node version to 16.x as 12 is EOL

[changeset-bot]

⚠️ No Changeset found

Latest commit: 42f1c10

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