fix(parser): resolve five high impact parser issues

[fglock]

Summary

Resolve the five selected high-impact issues labeled area:parser in this PR:

• Fix HTML::Tree 5.07 incremental split parsing mishandles chunk boundaries #1619: preserve decoded text, entities, and whitespace across incremental HTML input, including the HTML::TreeBuilder decode alias on the interpreter backend.
• Fix Allow ascending use VERSION declarations in one lexical scope #1622: allow ascending use VERSION declarations within a scope.
• Fix Valid prototype \@;@ incorrectly emits illegalproto warning #1615: accept the valid optional-array prototype \@;@ without a warning.
• Fix Parse all valid fully-qualified indirect constructor forms #1166: parse both reported fully qualified indirect-constructor forms.
• Fix Fix AnyEvent::Tools compilation and timer scheduling compatibility #1470: reduce AnyEvent callback dispatch work while preserving complete weak-reference cleanup; keep the upstream timing test unchanged.

The branch also retains regression coverage for #1466 and #1476, which were confirmed fixed on master and closed.

Validation

Tested source commit: d753a616e (rebased on current master; PR head adds documentation only).

• timeout 1800 nice -n 19 make: passed in 6m26s; all unit shards passed.
• nice -n 19 make check-links: passed.
• Label/pad regressions: 66/66 on standard Perl, JVM, and interpreter; Java label-registration test passed in the full build.
• Prototype, ascending-version, both qualified-constructor forms, and retained Parser rejects postfix method call on function-call result in HTML::Query dependency #1466/Accept escaped literals in Unicode transliteration replacement lists #1476 tests: 9/9 on standard Perl, JVM, and interpreter.
• HTML::Tree 5.07: 23 files on all three runtimes. JVM/interpreter each ran 989 assertions with one existing TODO failure; system Perl passed 969 tests and skipped the optional LeakTrace test. t/split.t passes 444/444 and t/refloop.t 8/8.
• License::SPDX 0.07: 35/35 tests across 10 files on JVM and interpreter.
• AnyEvent::Tools 0.12: unchanged mutex test passes 8/8; full suite passes 103/103 across seven files on standard Perl, JVM, and interpreter.

Dispatch work measurements are deterministic operation counts, not hardware retired instructions or host timing. The unchanged upstream tests were not modified.

Fixes #1619
Fixes #1622
Fixes #1615
Fixes #1166
Fixes #1470