RFR: 8305093: Linker cache should not take layout names into account

[Jorn Vernee]

Strip names from the function descriptors used in linkage requests. The names are not important for classification, and this will allow the cached MethodHandle/UpcallStubFactory to be shared across linkage request with the same structure, but with layouts that have different names.

I also have another implementation that avoids copying all the layouts, and instead re-implemented equals and hashCode in the LinkRequest wrapper: https://github.com/openjdk/jdk/compare/pr/13079...JornVernee:jdk:NoNameCache But, this seems too complex. Linking code is not very performance sensitive, so I instead went with a simpler approach in this patch.

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Depends on: https://git.openjdk.org/jdk/pull/13079

Commit messages:
 - re-add spuriously removed blank line
 - stripNames based caching

Changes: https://git.openjdk.org/jdk/pull/13562/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13562&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305093
  Stats: 93 lines in 2 files changed: 88 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13562.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13562/head:pull/13562

PR: https://git.openjdk.org/jdk/pull/13562