RFR: 8364570: Remove LockingMode related code from riscv64 [v3]

[Fredrik Bredberg]

> Since the integration of [JDK-8359437](https://bugs.openjdk.org/browse/JDK-8359437) the `LockingMode` flag can no longer be set by the user, instead it's declared as `const int LockingMode = LM_LIGHTWEIGHT;`. This means that we can now safely remove all `LockingMode` related code from all platforms.
> 
> This PR removes `LockingMode` related code from the **riscv64** platform.
> 
> When all the `LockingMode` code has been removed from all platforms, we can go on and remove it from shared (non-platform specific) files as well. And finally remove the `LockingMode` variable itself.

Fredrik Bredberg has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into 8364570_remove_lockingmode_riscv64
 - Update two after review
 - Update one after review
 - 8364570: Remove LockingMode related code from riscv64

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26658/files
  - new: https://git.openjdk.org/jdk/pull/26658/files/a32ae39e..0b244704

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26658&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26658&range=01-02

  Stats: 26689 lines in 690 files changed: 16193 ins; 8269 del; 2227 mod
  Patch: https://git.openjdk.org/jdk/pull/26658.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26658/head:pull/26658

PR: https://git.openjdk.org/jdk/pull/26658