ci: Enables opt-in wasm CI build for sql-kit

[scottmarchant]

⚠️ This PR is blocked from final testing and merging until dependent PR's are both merged and released. I added issues to the diff that I will resolve once everything is ready to resolve.

Change summary

Added swift wasm as a opt-in CI target, to help prevent future breakages to swift wasm builds.

This PR is part of a larger effort by PassiveLogic to add wasm support to many popular repositories.

Notes

• CI for this won't pass until a future swift-nio version is ready. See details below.

PR Dependencies

The following PR's must be merged before this PR can be merged:

• https://github.com/apple/swift-nio/pull/3271 (already merged, waiting for new swift-nio release)
• https://github.com/vapor/ci/pull/54
• https://github.com/vapor/sql-kit/pull/190

Testing done

Verified this new workflow functions correctly using a temporary PR that enables the new wasm build.

See https://github.com/PassiveLogic/sql-kit/actions/runs/15886122859/job/44798410586?pr=1

Remaining work

• [ ] Run tests on this once all dependent PR's are merged and released.