RFR: 8335110: Fix instruction name and API spec inconsistencies in CodeBuilder

[Chen Liang]

This is a collection of fixes and improvements to CodeBuilder, plus 2 renames.

Fixes include:
1. `CodeBuilder::receiverSlot` typo
2. `CodeAttribute::labelToBci` update spec
3. `CodeBuilder::exceptionCatch` implementation
4. `CodeBuilder::if_nonnull`/`if_null` -> `ifnonnull`/`ifnull`
5. Docs for what instructions factories emit, and to explain why some factories have name mismatch; also a section in summary.

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Commit messages:
 - Describe extra types of instructions that can be generated
 - Minor polishing to CodeBuilder

Changes: https://git.openjdk.org/jdk/pull/19889/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19889&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335110
  Stats: 123 lines in 6 files changed: 106 ins; 1 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/19889.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19889/head:pull/19889

PR: https://git.openjdk.org/jdk/pull/19889