Plumb memory heuristics into OpenJdk

Promote TokenizedVersion to be a top-level class. Use TokenizedVersion
to test the JRE version number in OpenJdk.

Modify the OpenJdk class to use the appropriate memory heuristic
based on the JRE version.

Move the memory heuristics classes into the JavaBuildpack::Jre module.

Fix up various tests to set $MEMORY_LIMIT as this is needed by the
memory heuristics.

Change the configured memory heuristic weightings to more reasonable
values: heap = 0.75, permgen/metaspace = 0.1, stack = 0.05, native =
0.05.

Add test for OpenJdk metaspace.

[#49694523]
Merge 49694523-default-sizes-formula to master

[Completes #49694523]