RFR: 8336103: Sharper checks for <init> and <clinit> initializers

[Aleksey Shipilev]

All around Hotspot, we have calls to `method->is_initializer()`. That method test for both instance and static initializers. In many cases, the uses imply we actually want to test for constructor (instance initializer), not static initializer. Sometimes we filter explicitly for `!m->is_static()`, sometimes we don't. Often we get lucky by never being exposed to static initializers on particular paths.

I would like to sharpen this. I went back and forth, and ultimately decided to remove `is_initializer` completely to avoid future confusion, and rewrite the uses appropriately.

Additional testing:
 - [x] Linux AArch64 server fastdebug, `all` (includes Fuzzer and CTW tests)

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

Commit messages:
 - Minor touchups
 - Relax MemberName, accept clinit as Method
 - Fix

Changes: https://git.openjdk.org/jdk/pull/20120/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20120&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336103
  Stats: 46 lines in 15 files changed: 10 ins; 17 del; 19 mod
  Patch: https://git.openjdk.org/jdk/pull/20120.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20120/head:pull/20120

PR: https://git.openjdk.org/jdk/pull/20120