test: make all-chain collections coverage opt-in

[omerbek]

Closes #1986.

What changed

• Replace the unconditional skip on the all-chain getCollections integration test with an explicit OPENSEA_RUN_ALL_CHAIN_COLLECTIONS=true gate.

Why

The test remains disabled by default for normal integration runs, but it is no longer permanently unreachable. Maintainers can enable the broader chain coverage in scheduled/manual CI or when validating multi-chain API behavior.

Testing

• git diff --check
• npm run test -- --run test/integration/getCollection.spec.ts could not run because dependencies are not installed locally (vitest not found).

[ryanio]

Thanks! Agreed on the reasoning: a permanently unreachable test.skip gives no coverage and no way to get any, so an explicit env gate is the right shape.

Recreated internally with you credited as co-author, and it's merged. The gate is OPENSEA_RUN_ALL_CHAIN_COLLECTIONS=true, matching your PR.

No concern about you not being able to run the suite locally, we ran it: 794 unit tests pass. Closing #1986 along with this.