RFR: 8313421: [JVMCI] avoid locking class loader in CompilerToVM.lookupType

[Doug Simon]

This PR removes the need to lock the system class loader when converting Class instances for boot and platform classes to ResolvedJavaType objects. Not only is the system class loader a suboptimal loader for resolving these classes but locking it can cause deadlock in some JDK tests (e.g. `test/jdk/java/lang/System/LoggerFinder/`) when run with `-Xcomp`. For example, a thread that holds the system class loader lock and triggers a blocking compilation will deadlock with the compiler thread servicing the compilation if the compilation requires calling `CompilerToVM.lookupType` (which most compilations do).

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Commit messages:
 - avoid locking class loader in CompilerToVM.lookupType (JDK-8313421)

Changes: https://git.openjdk.org/jdk/pull/15128/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15128&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313421
  Stats: 93 lines in 8 files changed: 41 ins; 19 del; 33 mod
  Patch: https://git.openjdk.org/jdk/pull/15128.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15128/head:pull/15128

PR: https://git.openjdk.org/jdk/pull/15128