RFR: 8340353: Remove CompressedOops::ptrs_base

[Kim Barrett]

Please review this change that

(1) Removes CompressedOops::ptrs_base(), changing all callers to instead call
CompressedOops::base().

(2) Renames CompressedOops::ptrs_base_addr() to CompressedOops::base_addr(),
updating all callers.

Testing:
mach5 tier1
GHA to test building on non-Oracle supported platforms

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Commit messages:
 - ptrs_base_addr => base_addr

Changes: https://git.openjdk.org/jdk/pull/21060/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21060&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340353
  Stats: 14 lines in 5 files changed: 1 ins; 3 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/21060.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21060/head:pull/21060

PR: https://git.openjdk.org/jdk/pull/21060