Clear the GroovyClassLoader cache before compiling

Since we don't use the cache, it's okay to clear it entirely if needed,
Elasticsearch maintains its own cache for compiled scripts.

Adds loader.clearCache() into a listener, the listener is called when a
script is removed from the Guava cache.

This also lowers the amount of cached scripts to 100, since 500 is
around the limit some users have run into before hitting an out of
memory error in permgem.

Fixes #7658
[CORE] Remove leftover unused constants
Tests: Add more logging to ExistsMissingTests.
Docs: Update object-type.asciidoc to make object type more explicit

Closes #7646
Internal: Fix serialization of PendingClusterTask.timeInQueue.

This parameter is serialized as a vLong while it could sometimes be negative.

Close #8077
Docs: Added elasticsearch-dsl-py

Closes #7812
Closes #7813
fix mismatched curly bracket
Docs: Fix (another) Idaho spelling

Closes #7912