RFR: 8343430: RISC-V: C2: Remove old trampoline call [v8]

[Fei Yang]

> Hi, please consider this cleanup change.
> 
> The old trampoline call on linux-riscv64 is disabled by default after: https://bugs.openjdk.org/browse/JDK-8332689.
> And the new solution (load target address from stub and call) has been baked in jdk master for quite some time.
> This propose to remove the old trampoline call related logic so that the code will be cleaner and easier to maintain.
> As we are still using `trampoline_stub_Relocation` for the stub, I kept using the original `emit_trampoline_stub` name.
> 
> Testing on linux-riscv64:
> - [x] tier1-tier3 (release)
> - [x] hotspot:tier1 (fastdebug)

Fei Yang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 12 commits:

 - Merge remote-tracking branch 'upstream/master' into JDK-8343430
 - More Comments
 - Merge remote-tracking branch 'upstream/master' into JDK-8343430
 - More naming
 - More improvements
 - Minor
 - More comments
 - Comment
 - Improve
 - Code comment
 - ... and 2 more: https://git.openjdk.org/jdk/compare/2989d873...11442458

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Changes: https://git.openjdk.org/jdk/pull/21822/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21822&range=07
  Stats: 632 lines in 12 files changed: 9 ins; 546 del; 77 mod
  Patch: https://git.openjdk.org/jdk/pull/21822.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21822/head:pull/21822

PR: https://git.openjdk.org/jdk/pull/21822