RFR: 8248186: Move CDS C++ vtable code to cppVtables.cpp [v2]

[Ioi Lam]

> I moved the code that supports C++ vtables in the CDS archive from metaspaceShared.cpp to a new file, cppVtables.cpp.
> To keep the refactoring straightforward, the code is moved verbatim, except for:
> - Methods are renamed from `MetaspaceShared::xx` to `CppVtables::xx`
> - Access to `_mc_region` is changed to the inline function `mc_region()`

Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains
two commits:

 - Merge branch 'master' into 8248186-refactor-cds-cpp-vtables
 - 8248186: Move CDS C++ vtable code to cppVtables.cpp

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Changes: https://git.openjdk.java.net/jdk/pull/136/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=136&range=01
  Stats: 696 lines in 7 files changed: 384 ins; 305 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/136.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/136/head:pull/136

PR: https://git.openjdk.java.net/jdk/pull/136