RFR: 8312262: Klass::array_klass() should return ArrayKlass pointer [v3]

[Coleen Phillimore]

> This is a simple change to make array_klass() return ArrayKlass (the first dimension of TypeArrayKlass is a TypeArrayKlass so can't use ObjArrayKlass), higher_dimension is always an ObjArrayKlass and lower_dimension can be a TypeArrayKlass.  The change removes some casts.
> Tested with tier1 linux/macosx/windows on x86 and aarch64.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Add back set_higher_dimension

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15059/files
  - new: https://git.openjdk.org/jdk/pull/15059/files/a9a9eb50..33a29f45

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15059&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15059&range=01-02

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15059.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15059/head:pull/15059

PR: https://git.openjdk.org/jdk/pull/15059