RFR: 8293291: Simplify relocation of native pointers in archive heap [v2]

[Ioi Lam]

> Some objects in the archive heap contain native pointers. E.g., archived `java.lang.Class` objects contain a pointer to its `Klass*`.
> 
> At runtime, if the archived metadata are mapped at an alternative address, all of the `Klass*` pointers must be relocated. Instead of doing this in an ad-hoc way, this PR uses a bitmap, `FileMapRegion::ptrmap_view()`, to track the position of all the native pointers.
> 
> This PR is done in preparation for supporting new types of archived heap objects that have native pointers. E.g., `java.lang.invoke.ResolvedMethodName` has a pointer to a `Method*`.
> 
> 
> Notes for reviewers:
> 
> - At dump time, the native pointers are remembered in `HeapShared::mark_native_pointers()`.
> - At runtime, the native pointers are patched in `ArchiveHeapLoader::patch_native_pointers()`.
> - The ad-hoc relocation code has been removed from javaClasses.cpp and systemDictionaryShared.cpp
> - Many of the changes are for renaming from "oopmaps" to "bitmaps": the old code handled only a single type of pointers (oop references). The new code handles two types of bitmaps ("oopmap" is for oop references, "ptrmap" is for native pointers).

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @calvinccheung comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10296/files
  - new: https://git.openjdk.org/jdk/pull/10296/files/4eee5962..24b905b3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10296&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10296&range=00-01

  Stats: 6 lines in 4 files changed: 1 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/10296.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10296/head:pull/10296

PR: https://git.openjdk.org/jdk/pull/10296