Feature #2334 land_mask (and topo_mask) in PointStat

Pull Request Testing

[X] Describe testing already performed for these changes:
Added new unit tests
Set new config variables in PointStat.conf and confirmed that use case ran successfully with values set
[X] Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
Review documentation updates
Confirm new config variables can be used in use case that warranted opening the issue
[X] Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes]
[X] Do these changes include sufficient testing updates? [Yes]
[X] Will this PR result in changes to the test suite? [No]
[X] Please complete this pull request review by 1/10/2024.

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[X] Add any new Python packages to the METplus Components Python Requirements table.
[X] Review the source issue metadata (required labels, projects, and milestone).
[X] Complete the PR definition above.
[X] Ensure the PR title matches the feature or bugfix branch name.
[X] Define the PR metadata, as permissions allow. Select: Reviewer(s) Select: Organization level software support Project or Repository level development cycle Project Select: Milestone as the version that will include these changes
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[ ] After the PR is approved, merge your changes. If permissions do not allow this, request that the reviewer do the merge.
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