[AUDIO_WORKLET] Enable AW spinlocks, verify them in the browser tests (…

…emscripten-core#23729)

- spinlocks fixed so they work in audio worklets
- adds tests for various spinlock cases
- test converted to C-only (still in a C++ file for now, see below)

This was unmerged last year (emscripten-core#22995), visited again now the browser
tests are running with audio. It's been moved over to `btest_exit()` and
verified that it runs (and will only exit after all tests have run or
asserted).

The only change I'd make is to rename the original test file, which has
grown beyond its original use. A `git mv` command won't survive multiple
commits, so I want to either leave it until last, live with the
resulting deletion, or rename as a separate PR.

Fixes: emscripten-core#22962

Simplify EGL/GLFW/SDL/GLUT/Browser canvas access. NFC (emscripten-cor…

…e#23614)

All of these frameworks still use `Module['canvas']`. This change
simplifies and unifies the access to the canvas to single helper
function per library.

As a followup we may want to extend this to all use of
`Module['canvas']`.

[embind] Stricter function argument name checking (emscripten-core#23524

)

Distinguish between unknown argument list and the empty argument list
when parsing function names.

Also use early return to make the code a little more compact.

[emcc.py] Remove unused function. NFC (emscripten-core#23429)

This should have been removed as part of emscripten-core#20917.

Run test_chmod in nodefs. NFC (emscripten-core#23230)

Catches a bug in `lchmod` in NODEFS. The fix will be quite simple after
emscripten-core#23058 is merged.

Use async/await for internal readAsync function. NFC (emscripten-core…

…#23120)

Followup to emscripten-core#23104.

 [nodefs] Return real values for statvfs via __syscall_statfs64 emscr…

…ipten-core#22631  (emscripten-core#22932)

statfs syscall functions are returning hardcoded default values which
can in some cases lead to unexpected results.

This PR introduces a way for __syscall_statfs64 to return real values if
the underlying filesystem supports this. For now, I've only implemented
this for the NODEFS filesystem but we can expand this to other
filesystems when it makes sense.

Additionally, in the previous defaults, ffree could be larger than files
which is incorrect, this has also been addressed.

Fixes: emscripten-core#22607

Make seek work on `/dev/null` (emscripten-core#22886)

Seeking `/dev/null` should work and do nothing instead of returning
`EPIPE`. This fixes it.

Add an optimized variant of test_split_module (emscripten-core#22833)

This ensures that the test works on optimized binaries with export
minification.

WebIDL Binder: Allow all binary C++ operators (emscripten-core#22770)

This expands the list of supported operators by the 'Operator' WebIDL
attribute to all binary operators that are supported by C++.

Helps emscripten-core#9415