RFR: 8339132: Make DirectCodeBuilder write through without allocating instruction objects [v3]

[Chen Liang]

> Make `DirectCodeBuilder` write instructions actually directly without allocating extra objects. This speed up a lot of simple Class-File building cases that never go through intermediate transforms.

Chen Liang 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 five additional commits since the last revision:

 - Remove redundant qualification, avoid boxing in b/sipush validation
 - Merge branch 'master' of https://github.com/openjdk/jdk into exp/cob-direct-methods
 - Use uppercase L for long literals
   
   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
 - Moar fixes
 - More direct code builder

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20738/files
  - new: https://git.openjdk.org/jdk/pull/20738/files/d798b302..a12992d2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20738&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20738&range=01-02

  Stats: 2927 lines in 47 files changed: 1943 ins; 509 del; 475 mod
  Patch: https://git.openjdk.org/jdk/pull/20738.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20738/head:pull/20738

PR: https://git.openjdk.org/jdk/pull/20738