[RFR] 8344140: Refactor the discovery of AOT cache artifacts

[ioi.lam at oracle.com]

FYI - This is a PR for the JDK mainline related to Leyden development. 
Please comment on the PR page:

https://github.com/openjdk/jdk/pull/22291


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This is a clean up after the initial integration for JEP 483

+ Merged 3 loops into 1 for discovering the classes and oops that should
   be stored in the AOT cache. About 250 lines of code are deleted.

+ Added comments in aotArtifactFinder.hpp to describe the logic, which
   is much simpler than before.

+ Enum classes are no longer unconditionally AOT-initialized -- an Enum
   class is AOT-initialized only if we find an archived oop of this type.

Note to reviewers:

One consequence of this refactoring is that archived oops are now
discovered (by heapShared.cpp) before the metadata are copied (by 
ArchiveBuilder).
There are some functions that depend on the old order (metadata were copied
before oop discovery), so I had to shuffle them around. Examples are
Modules::check_archived_module_oop(), or the new code in 
Klass::remove_java_mirror().