gh-155358: Convert sys structseq types to heap types

[vstinner]

Convert the following structseq types from static (built-in) types to heap types:

• AsyncGenHooksType
• Hash_InfoType
• WindowsVersionType
• FlagsType
• VersionInfoType

So these types are no longer shared between sub-interpreters.

Cleanup also the EmscriptenInfoType type.

Changes:

• Replace _PyStructSequence_InitBuiltin() with PyStructSequence_NewType() or _PyStructSequence_NewType().
• Add PyInterpreterState.sys_state structure.
• Rename sys.get_asyncgen_hooks() type from "asyncgen_hooks" to "sys.asyncgen_hooks".
• Add test.support.check_immutable_type().

• Issue: Deprecate the tuple API (object[index]) of structseq types (ex: os.stat_result) #155358

[vstinner]

If this change is merged, it would be interesting to convert the following 4 static types to heap types as well:

Objects/floatobject.c:    if (_PyStructSequence_InitBuiltin(interp, &FloatInfoType,
Objects/longobject.c:    if (_PyStructSequence_InitBuiltin(interp, &Int_InfoType,
Python/errors.c:    if (_PyStructSequence_InitBuiltin(interp, &UnraisableHookArgsType,
Python/thread.c:    if (_PyStructSequence_InitBuiltin(interp, &ThreadInfoType, &threadinfo_desc) < 0) {

[vstinner]

So these types are no longer shared between sub-interpreters.

I discovered later that these types are immutable, so I'm not sure that it's a big deal to share these static types between sub-interpreters.

This change is mostly needed if issue gh-155358 is accepted. For now, I prefer to close the PR, since it doesn't need to be strictly needed (if the issue is not accepted).

I already pushed the uncontroversial part of this change as a separated PR: PR gh-155510 checks that 5 sys types, such as type(sys.flags), are immutable (and add test.support.check_immutable_type() helper function).