RFR: 8342561: Metaspace for generated reflection classes is no longer needed

[Coleen Phillimore]

Removed code and test for the special metaspace size for reflection DelegatingClassLoader which only had one class.  Now that it's gone, we don't need the special size.  I changed some of the test cases to use ClassMirrorHolderMetaspaceType as a smaller alternate type instead and the tests seem fine with that.
Tested with tier1-4

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Commit messages:
 - 8342561: Metaspace for generated reflection classes is no longer needed

Changes: https://git.openjdk.org/jdk/pull/21738/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21738&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342561
  Stats: 52 lines in 7 files changed: 3 ins; 39 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/21738.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21738/head:pull/21738

PR: https://git.openjdk.org/jdk/pull/21738