Optimize the shared leaf memory pool locking

[xiaoxmeng]

Avoid the global locking when access shared leaf memory pool:

1. remove the global lock access to the single-ton memory manager
2. remove the global lock to access shared leaf pool array

Next step is to work with Meta internal teams to deprecate such use cases with explicit leaf memory pool lifecycle management at user side as well as explicit memory manager initialization.

[netlify[bot]]

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[facebook-github-bot]

@xiaoxmeng has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@xiaoxmeng has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@xiaoxmeng has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@xiaoxmeng has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@xiaoxmeng has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D57405421

[facebook-github-bot]

@xiaoxmeng merged this pull request in facebookincubator/velox@2b94547ea972b38adaad54c2d8b014f62cb587b8.

[conbench-facebook[bot]]

Conbench analyzed the 1 benchmark run on commit 2b94547e.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details.