RFR: 8313530: VM build without C2 fails after JDK-8312579 [v2]

[Gergö Barany]

> The EnableVectorSupport flag is declared in `opto/c2_globals.hpp`, which is not included if `COMPILER2` is not set. But after my changes for [JDK-8312579](https://bugs.openjdk.org/browse/JDK-8312579) we try to access this flag in some places guarded by `#if COMPILER2_OR_JVMCI`.
> 
> This PR moves some flags from `c2_globals.hpp` to the shared `compiler_globals.hpp`, so that they are accessible even if C2 is disabled but JVMCI is enabled.

Gergö Barany has updated the pull request incrementally with two additional commits since the last revision:

 - Add copies of Vector API flags in jvmci_globals.hpp
 - Revert "8313530: VM build without C2 fails after JDK-8312579"
   
   This reverts commit d82e89c469e91f78f9c2e5b28c725b0e1ba0fb8c.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15384/files
  - new: https://git.openjdk.org/jdk/pull/15384/files/d82e89c4..278e5e51

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15384&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15384&range=00-01

  Stats: 39 lines in 3 files changed: 24 ins; 14 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15384.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15384/head:pull/15384

PR: https://git.openjdk.org/jdk/pull/15384