Fix compiler and tooling compatibility for CPAN modules

[fglock]

Summary

• fix fixed-prototype trailing commas before boolean infix operators
• preserve caller DATA handles and file ownership of end-of-scope callbacks across nested loads
• retain tied handlers during reachability sweeps and complete DBI metadata statement behavior
• tighten the IO::Async distropref and preserve DateTime::Format::Builder generated methods
• add system-Perl-compatible regression coverage and a completed compatibility design note

Requested distribution results

Distribution	Result
Net::Async::SMTP	PASS: 3 files, 18 tests
Group::Git	PASS: 7 files, 43 tests
Locale::CLDR::Locales::Lu	PASS: 1 file, 4 tests
Dist::Zilla::Plugin::Meta::Maintainers	PASS: 2 files, 2 tests
TOML::Tiny	PASS: 291 files, 484 tests
DBIx::Admin::BackupRestore	PASS: 4 files, 15 tests
Number::Phone::NO	PASS: 10 files, 23 tests
WWW::Wikipedia	Excluded: its live-API suite also fails under system Perl (13 files, 45 tests, exit 1)

Number::Phone::NO passes, although JVM teardown can emit a non-fatal stack overflow while cleaning the large DBM::Deep object graph. The design note records this separately for future iterative teardown work.

Validation

• prove with system Perl: 5 focused files, 20 tests, PASS
• make: PASS (BUILD SUCCESSFUL, all five unit-test shards)