fix(compiler): regex/super/dynamic-import in async & generator bodies (#1105)

[nickna]

Closes #1105.

Problem (reproduced firsthand)

A regex literal, super.x, or import() inside an async function / function* body silently compiled to null in compiled mode — wrong result at runtime, no error:

async function asyncRegex() { const re = /ab+c/; return re.test("abbbc"); }
function*    genRegex()   { const re = /xy+z/; yield re.test("xyyyz"); }

Interpreted: true / true. Compiled (before): false / false.

Root cause

The four state-machine emitters (async / async-arrow / generator / async-generator) derive from StatementEmitterBase, not ILEmitter, so they inherited a base EmitRegexLiteral that pushed Ldnull. The generator emitters additionally overrode EmitSuper/EmitDynamicImport to push null. The real implementations existed only in ILEmitter. The "base default pushes null, override only in ILEmitter" pattern guaranteed every such expression kind silently miscompiled in a state-machine body.

Fix

• Regex — ported the full hoist-aware $RegExp emission from ILEmitter into the shared ExpressionEmitterBase.EmitRegexLiteral. The per-site hoist fields already hang off the shared EmittedRuntime, so it needs no sync-only state. Removed the now-redundant ILEmitter override. Regex now compiles identically in functions, arrows, and all four state machines.
• super — removed the silent-null EmitSuper overrides in GeneratorMoveNextEmitter and AsyncGeneratorMoveNextEmitter. The base default (load hoisted this → GetSuperMethod, which resolves via the instance's runtime base type) works in the state machine. Verified super.x in generators and async generators now matches interpreted output and the existing async-function behavior.
• dynamic import — removed the silent-null EmitDynamicImport override in GeneratorMoveNextEmitter. The base default routes through the module registry, behaving identically to async functions. (The remaining "module not pre-compiled" error is an orthogonal compiled-mode bundling limitation that affects async functions the same way — not state-machine-specific, so no super/import follow-up is needed.)
• Tests — updated the EmitterSyncTests allowlist (removed the three stale override entries) and added 8 DifferentialParityTests snippets pinning regex/super across the four bodies (each snippet runs through both interpreter and compiler and asserts identical output).

Note: contrary to the issue's "make the base virtuals throw a CompileException + file follow-ups" suggestion, super actually works through the base default in state machines — so making them work beat failing loud, and no feature-gap follow-up is required.

Verification

• Full xUnit suite: 14519 passed / 0 failed / 16 skipped (skips are pre-existing network/package smoke tests).
• EmitterSyncTests (2) + DifferentialParityTests (91, incl. 8 new) green.
• All manual repros show interp == compiled for regex/super in every state-machine body.
• The Test262 CompiledBaseline test host-crashes here (Internal CLR error 0x80131506) under both parallel and SHARPTS_TEST262_WORKERS=1 — confirmed pre-existing by stashing to clean main (same crash), so unrelated to this change. The committed subset's RegExp folder is top-level regex = byte-identical IL.