8373266: Strengthen constant CardTable base accesses

[shipilev]

Shenandoah and G1 are using CardTable for most of its infrastructure, but flip the card tables as they go, and maintain the actual card table reference in TLS. As such, accessing card table base from assembler and compilers runs into risk of accidentally encoding the wrong card table base in generated code.

Most of the current code avoids this trouble by carefully implementing their GC barriers to avoid touching shared parts where card table base constness is assumed. Except for JVMCI, that reads the card table base for G1 barrier set, and that is wrong. The JVMCI users would need to rectify this downstream.

Shenandoah added a few asserts to catch these errors: SHENANDOAHGC_ONLY(assert(!UseShenandoahGC, "Shenandoah byte_map_base is not constant.");)

...but G1 would also benefit from the similar safety mechanism.

This PR strengthens the code to prevent future accidents.

Additional testing:

• [x] Linux x86_64 server fastdebug, hotspot_gc
• [x] Linux x86_64 server fastdebug, all with Serial, Parallel, G1, Shenandoah, Z
• [x] Linux AArch64 server fastdebug, all with Serial, Parallel, G1, Shenandoah, Z
• [x] GHA, cross-compilation only

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Progress

• [ ] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• [x] Commit message must refer to an issue

Issue

• JDK-8373266: Strengthen constant CardTable base accesses (Enhancement - P4)

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Webrevs

• 00: Full (26b6b071)

[shipilev]

all tests are passing with various GC combinations as well. Ready for review.