Avoid unaligned packed index accesses

[justinblethrow-cloud]

Summary

• Replace unaligned typed loads and stores in PackedArray with fixed-size memcpy operations.
• Apply the same treatment to packed suffix loads used during genome generation and suffix-array search.
• Add an odd-address ASan/UBSan regression test.

Problem

STAR intentionally packs arrays at byte-granular offsets, but several accessors cast those addresses to uint64_t* or uint128* and dereference them. These operations are undefined on unaligned addresses and are reported during both index generation and mapping by UBSan.

Validation

• extras/tests/scripts/testPackedArray.sh passes; its odd-address case reports a misaligned access against unmodified 2.7.11b.
• A full ASan/UBSan build succeeds.
• Tiny annotated genomeGenerate completes with UBSAN_OPTIONS=halt_on_error=1.
• Fourteen core genome and annotation artifacts, including Genome, SA, SAindex, chromosome metadata, gene/transcript/exon tables, and SJDB files, are byte-identical to unmodified 2.7.11b.