[AUDIO_WORKLET] Added support for MEMORY64 and 2GB heap (including tests)

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This is built on #22753 and uses the _2gb and _4gb tests (plus the parameter test) from #23659.

It adds support for MEMORY64 to audio worklets and tests that:

• All the pointer offsets and maths now work with >2GB heap
• Everything works building with MEMORY64 and >4GB heap

The tests already prove out various buffer combinations using the INITIAL_MEMORY and GLOBAL_BASE flags.

For the code changes, besides parameters expecting BigInt it also needed any shifts removing from the offset calculations (signed shifts fail >2GB, unsigned >4GB).

The interactive tests (from #23659) can be run with:

test/runner.py interactive_2gb.test_audio_worklet_params_mixing
test/runner.py interactive64_4gb.test_audio_worklet_params_mixing

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I wrote a test for the web audio parameters, creating a pair of descriptors and using the first to handle fading. It needs some tidying up but the important parts are done and it correctly gets the C structs to JS. Demo here:

https://wip.numfum.com/cw/2025-02-05/index.html

It only properly works in Chrome and Firefox so far (I'll look at it).

This single line does the fade-in/out:

emscripten/test/webaudio/audioworklet_params_mixing.c

Line 59 in 48361fd

param.setTargetAtTime((param.value > 0.5) ? 0 : 1, 0 /* same as context.currentTime */, 0.5);

And the mix is currently done with this:

emscripten/test/webaudio/audioworklet_params_mixing.c

Line 42 in 48361fd

outputData[i] += inputData[i] * params[0].data[(params[0].length > 1) ? i : 0]; // world's worst mixer...

As before, @sbc100, shall I create a new PR just for these tests? Then another PR that fixes running the tests? Tests moved to #23659, work started on fixing the browser tests.

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What about the exsiting audio worklet tests in test_browser.py?

All the AW tests are silently failing. I'll look at fixing them next.

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It looks like we already have interactive64 mode in test_interactive.py. Can you just add interactive64_4gb and interactive_2gb modes? (copy them from test_browser.py).

Done.

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Note for me to look at (POINTER_TYPE and POINTER_SIZE):