RFR: 8294187: RISC-V: Unify all relocations for the backend into AbstractAssembler::relocate() [v2]

[Xiaolin Zheng]

> Unify all relocations into AbstractAssembler::relocate() as a simple cleanup.
> 
> Tested hotspot tier1 and tier2 on QEMU.

Xiaolin Zheng has updated the pull request incrementally with two additional commits since the last revision:

 - Migrate them to the next patch for AbstractAssembler has their counterparts
 - Remove useless add_debug_info_for_branch(adr, CodeEmitInfo*)

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10384/files
  - new: https://git.openjdk.org/jdk/pull/10384/files/21ba6a61..a33331e1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10384&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10384&range=00-01

  Stats: 27 lines in 3 files changed: 0 ins; 27 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10384.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10384/head:pull/10384

PR: https://git.openjdk.org/jdk/pull/10384