Build and test the SILK NEON kernel in CI

[hashirmuzaffar]

Fixes #240.

The parity test from #243 exists, but nothing in CI ever assembles the kernel it covers. The build tag is arm64 && go1.27 && !purego; the matrix in test.yaml is on the supported release list, so test-macos is arm64 on an older Go and the newer-Go jobs are amd64. The file is never built and the test never runs.

I did not change test.yaml. It carries a DO NOT EDIT header and is synced from pion/.goassets, so an edit here would be reverted, and raising the shared matrix would move every pion repository onto a newer Go to cover one kernel in this one. conformance.yml, encoder-quality.yml and plc-quality.yml are already repo-local, so this follows that pattern.

The job does three things:

1. Asserts the kernel is in the build before testing anything. This is the part that matters — without it, a build tag that stopped matching would leave the job green while compiling nothing, which is exactly the situation the issue describes. It inspects go list output for iir_fir_arm64.s and fails with an error annotation if it is absent.
2. Runs the parity test under -race.
3. Runs the package again under -tags purego, so the generic path stays covered on the same runner.

Verified locally on arm64 with Go 1.27:

go list ... ./internal/resample/silk   ->  iir_fir.go iir_fir_arm64.go iir_fir_arm64.s
TestIIRFIRInterpolateNEONMatchesGeneric      PASS
TestIIRFIRInterpolateNEONCoversEveryPhase    PASS
TestIIRFIRInterpolateAccumulatorBound        PASS

go list -tags purego ...                ->  iir_fir.go iir_fir_generic.go
go test -tags purego ...                     ok

The guard behaves as intended under purego: the kernel is correctly absent, which is what would fail the job if the tag ever stopped matching in the NEON configuration.

If you would rather take the matrix change discussed in the issue thread, 1.24/1.27 on test-macos, that belongs in .goassets and I am happy to send it there instead.

[JoTurk]

We manage the ci in one repo in goassets, soon we'll change our test matrix to include 1.27 in the next ci update