[Feature]: simple land-sea mask generation

[lee1043]

Is your feature request related to a problem?

Bringing in the land-sea mask generation capability that was built using regionmask into the PMP, unless it will be implemented to xcdat.

Describe the solution you'd like

The working code is described here: xCDAT/xcdat#576

Describe alternatives you've considered

Using pcmdi_utils have been considered as an alternative place to host such capabilities, but currently one of its dependencies, global-land-mask, is only available through pip, complicating the conda installation process.

Additional context

Hosting this capability will also help addressing #1004 and potential issues from other similar codes.

[lee1043]

Just to leave a note:

The apply_landmask function is newly added which include create_land_sea_mask by using either of pcmdi method or regionmask.

By default apply-landmask is more strict in removing coastline grid, which tend to remove more of coastline grids.

Related test also can be found at: xCDAT/xcdat#613 (comment)