Data::Printer support: Phase 3-6 fixes

[fglock]

Summary

Improve Data::Printer module compatibility with a series of fixes across Phases 3-6. Data::Printer test results improved to 576/624 subtests passing (92.3%).

Phase 3 - B module stubs

• Add B::CV::ROOT (returns B::OP, all subs have bodies on JVM)
• Add B::CV::const_sv (returns \0 for non-constant subs)
• Add B::class() utility function (strips B:: prefix from ref)
• Add B::NULL package (for undefined/stub sub detection)
• Add B::SV::RV (unwraps one level of reference)

Phase 4 - Module fixes

• charnames::viacode: Add Charnames.java using ICU4J UCharacter.getName() with Perl fallback
• File::Temp: Export SEEK_SET/SEEK_CUR/SEEK_END with :seekable tag
• Glob tilde expansion: Add expandTilde() in ScalarGlobOperatorHelper, reads $ENV{HOME} first

Phase 5 - Tied variable ClassCastException fix

• Add instanceof guards in TieScalar.tiedDestroy() and tiedUntie()
• Fix TieOperators.untie() and tied() for proxy entries

Phase 6 - Multiple Data::Printer-specific fixes

• UNIVERSAL methods: Set code.packageName/code.subName in PerlModuleBase.registerMethod()
• $! dualvar: Change ErrnoVariable to use DUALVAR type with DualVar value, add local $! support
• Tied FETCH caching: Cache FETCH result in TieScalar.tiedFetch() so untie restores last fetched value
• Digest::SHA: Fix @isa to include Digest::base (was overwritten by subsequent assignment)

Remaining failures (48/624)

• ~28 subtests: Weak refs/refcount (fundamental JVM limitation)
• ~10 subtests: Profile type numbering differences
• 4 subtests: Read-only constant detection
• 2 subtests: B::Deparse (not implemented)
• 2 subtests: LVALUE ref detection
• 1 subtest: FORMAT ref, 1 DBI filter, 1 ContentType hex dump, 1 color test

Test plan

• make passes (all unit tests)
• Data::Printer test suite: 576/624 subtests passing (92.3%)
• $! dualvar works with and without local
• UNIVERSAL methods visible in class introspection
• Glob tilde expansion respects $ENV{HOME}
• Tied scalar untie restores FETCH result
• Digest::SHA recognized by Data::Printer Digest filter

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