RFR: 8371779: Replace MemTagBitmap with ResourceBitMap

[Johan Sjölen]

Hi,

This PR wraps the` MallocMemorySummary::_snapshot` in a `DeferredStatic`. This is not strictly necessary as MallocMemorySnapshot does not have a non-trivial constructor, but it does give us more consistency and does act as a safe guard for future changes. 

Testing: GHA

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Commit messages:
 - Defer static snapshot

Changes: https://git.openjdk.org/jdk/pull/28257/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28257&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371779
  Stats: 5 lines in 2 files changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/28257.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28257/head:pull/28257

PR: https://git.openjdk.org/jdk/pull/28257