RFR: 8345826: Do not automatically resolve jdk.internal.vm.ci when libgraal is used [v5]

[Doug Simon]

> The `EnableJVMCI` flag currently serves 2 purposes:
> * Guards VM code ([example](https://github.com/openjdk/jdk/blob/b1e778d9d2ad13ee5f1ed629a8805008580f86c0/src/hotspot/share/runtime/sharedRuntime.cpp#L652)).
> * [Adds](https://github.com/openjdk/jdk/blob/b1e778d9d2ad13ee5f1ed629a8805008580f86c0/src/hotspot/share/runtime/arguments.cpp#L1804) `jdk.internal.vm.ci` to the root module set.
> 
> This PR changes nothing about the first point.
> 
> On the second point, to use the `jdk.internal.vm.ci` module when libgraal is enabled, `--add-modules=jdk.internal.vm.ci` must be specified.
> If libgraal is not enabled, +EnableJVMCI will continue to add `jdk.internal.vm.ci` to the root module set.
> 
> The primary motivation is to make use of libgraal compatible with `-XX:+AOTClassLinking`. This flag relies on the root module set archive created in a training run. If the root module set is different in the production run, the AOTClassLinking [optimizations](https://bugs.openjdk.org/browse/JDK-8342279) are disabled. As `jdk.internal.vm.ci` is not resolved in the training run, it must not be resolved in production run. As such, `-XX:+EnableJVMCI` must not cause resolution of `jdk.internal.vm.ci`, otherwise libgraal will not have the startup advantages of AOTClassLinking.

Doug Simon has updated the pull request incrementally with two additional commits since the last revision:

 - load the JVMCI module if +EnableJVMCI is set on the command line
 - JAVA_NOT_ENABLED_ERROR_MESSAGE -> JVMCI_NOT_ENABLED_ERROR_MESSAGE

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25240/files
  - new: https://git.openjdk.org/jdk/pull/25240/files/1fe56b41..d9223afb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25240&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25240&range=03-04

  Stats: 15 lines in 6 files changed: 0 ins; 4 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/25240.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25240/head:pull/25240

PR: https://git.openjdk.org/jdk/pull/25240