RFR: 8356075: Support Shenandoah GC in JVMCI [v2]

[Roman Kennke]

> In order to support Shenandoah GC in Graal, some changes are required in JVMCI, namely, export Shenandoah relevant symbols.
> 
> Testing:
>  - [x] extensive testing with https://github.com/oracle/graal/pull/10904

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Initialize cardtable_start_address to nullptr

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/25001/files
  - new: https://git.openjdk.org/jdk/pull/25001/files/6487a9f7..c95313a9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25001&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25001&range=00-01

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25001.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25001/head:pull/25001

PR: https://git.openjdk.org/jdk/pull/25001