RFR: 8326959: Improve JVMCI option help

[Doug Simon]

This PR improves the wording of JVMCI options that should be exposed to users.
All other JVMCI options are no longer included in the output of `-XX:+JVMCIPrintProperties`.


> java -XX:+JVMCIPrintProperties
[JVMCI properties]
jvmci.Compiler = null                                                     [String]
          Selects the system compiler. This must match the getCompilerName() value returned by a jdk.vm.ci.runtime.JVMCICompilerFactory provider. An empty string or the value "null" selects a compiler that raises an exception upon receiving a compilation request.
jvmci.PrintConfig = false                                                [Boolean]
          Prints VM values (e.g. flags, constants, field offsets etc) exposed to JVMCI.

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Commit messages:
 - improve help text for some JVMCI options and removed help from internal options

Changes: https://git.openjdk.org/jdk/pull/18045/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18045&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326959
  Stats: 51 lines in 2 files changed: 27 ins; 2 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/18045.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18045/head:pull/18045

PR: https://git.openjdk.org/jdk/pull/18045