RFR: 8292286: Convert PlaceholderTable to ResourceHashtable

Fri Aug 12 13:14:51 UTC 2022

This change converts the PlaceholderTable to ResourceHashtable.  It's much like the ResolutionErrorTable conversion.  This change has been performance tested with the previous set of testing with no regression.  It's also been tested tier1-3 and 4-7 with the other tables in my patch queue.

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Commit messages:
 - 8292286: Convert PlaceholderTable to ResourceHashtable

Changes: https://git.openjdk.org/jdk/pull/9854/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9854&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292286
  Stats: 287 lines in 6 files changed: 35 ins; 151 del; 101 mod
  Patch: https://git.openjdk.org/jdk/pull/9854.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9854/head:pull/9854

PR: https://git.openjdk.org/jdk/pull/9854