RFR: 8267089: Use typedef KVHashtable for ID2KlassTable

[Yi Yang]

While backporting some stuff to jdk11, I noticed main functionalities of ID2KlassTable have been removed afterJDK-8213587, it seems that we can use a simple typedef KVHashtable instead.

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Commit messages:
 - use kvtable directly

Changes: https://git.openjdk.java.net/jdk/pull/4007/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4007&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267089
  Stats: 9 lines in 2 files changed: 3 ins; 5 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4007.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4007/head:pull/4007

PR: https://git.openjdk.java.net/jdk/pull/4007