RFR: 8288730: Add type parameter to Lookup::accessClass and Lookup::ensureInitialized [v2]

[Chen Liang]

> Parameterizes `Lookup::accessClass` and `Lookup::ensureInitialized`. Updated an applicable use-site within JDK to benefit from this patch.

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Update return spec to indicate the same targetClass object is returned

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12984/files
  - new: https://git.openjdk.org/jdk/pull/12984/files/e4dc34cb..3b7d8055

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12984&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12984&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12984.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/12984/head:pull/12984

PR: https://git.openjdk.org/jdk/pull/12984