RFR: 8332123: [nmt] Move mallocLimit code to the nmt subdir

[Sonia Zaldana Calles]

Hi all, 

This PR addresses [8332123](https://bugs.openjdk.org/browse/JDK-8332123) moving malloc limit code under the nmt subdirectory. 

Thanks, 
Sonia

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Commit messages:
 - 8332123: [nmt] Move mallocLimit code to the nmt subdir

Changes: https://git.openjdk.org/jdk/pull/19462/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19462&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332123
  Stats: 5 lines in 6 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/19462.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19462/head:pull/19462

PR: https://git.openjdk.org/jdk/pull/19462