RFR: 8337987: Relocate jfr and throw_exception stubs from StubGenerator to SharedRuntime [v4]

[Andrew Dinn]

> Store the throw_exception and jfr stub code as blobs in class SharedRuntime, move the generation code to the the arch-specific generator classes and update client code to access them from their new location.

Andrew Dinn has updated the pull request incrementally with one additional commit since the last revision:

  fix riscv port issues

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20566/files
  - new: https://git.openjdk.org/jdk/pull/20566/files/f12aea03..16482052

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20566&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20566&range=02-03

  Stats: 8 lines in 1 file changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20566.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20566/head:pull/20566

PR: https://git.openjdk.org/jdk/pull/20566