RFR: 8309603: Deallocate hashtables in ClassLoaderData::unload [v2]

[Chad Rakoczy]

> [JDK-8309603](https://bugs.openjdk.org/browse/JDK-8309603)
> 
> Memory is released in `ClassLoaderdata::~ClassLoaderData` for the dictionary and module hashtables but they could be deleted earlier in `ClassLoaderdata::unload`. Since we're unloading the class loader is no longer being used for lookup.
> 
> Additional testing:
> - [x] Linux x86_64 fastdebug `tier2`
> - [x] Linux x86_64 release `tier2`
> - [x] Linux x86_64 fastdebug `gtest:all`
> - [x] Linux x86_64 release `gtest:all`
> - [x] Linux x86_64 fastdebug `test/hotspot/jtreg/runtime`
> - [x] Linux x86_64 release `test/hotspot/jtreg/runtime`

Chad Rakoczy has updated the pull request incrementally with one additional commit since the last revision:

  Deallocate packages and unnamed module in unload

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14820/files
  - new: https://git.openjdk.org/jdk/pull/14820/files/8c3bbf87..289cc322

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14820&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14820&range=00-01

  Stats: 24 lines in 1 file changed: 12 ins; 12 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14820.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14820/head:pull/14820

PR: https://git.openjdk.org/jdk/pull/14820