RFR: 8339359: RISC-V: Use auipc explicitly in far_jump and far_call macro assembler routines

[Fei Yang]

Previous discussion: https://github.com/openjdk/jdk/pull/18942#issuecomment-2109162337

For MacroAssembler::far_call and MacroAssembler::far_jump, I would suggest we use explicit
auipc instead of MacroAssembler::la for them as the destination is ensured to be in code cache.
This will help save unnecessary check in MacroAssembler::la and make the code more consistent.
Also this will help distinguish these two macro assembler routines from MacroAssembler::rt_call

Testing:
- [ ] release & fastdebug builds
- [ ] Tiered 1-3 tests

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Commit messages:
 - 8339359: RISC-V: Use auipc explicitly in far_jump and far_call macro assembler routines

Changes: https://git.openjdk.org/jdk/pull/20805/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20805&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339359
  Stats: 11 lines in 1 file changed: 7 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20805.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20805/head:pull/20805

PR: https://git.openjdk.org/jdk/pull/20805