pygmt.triangulate: Refactor to use codes consistent with other wrappers

[seisman]

Description of proposed changes

The triangulate module was first wrapped in PR #731. As mentioned in PR #731:

The complicated thing about triangulate is that it generates either text (table) or NetCDF (grid) outputs, and I've implemented it similar to grdhisteq at #1433 as so:

• triangulate.delaunay_triples:
  • When output_type="numpy", output table as numpy.ndarray
  • When output_type="pandas" (default for table), output table as pandas.DataFrame
  • When output_type="file" and outfile is not None, output table as textfile
• triangulate.regular_grid:
  • When outgrid=True (default for grid), output grid as 'xarray.DataArray`
  • When outgrid="test.nc", output grid to NetCDF file

So, in PR #731, a private function _triangulate was implemented and was internally called by triangulate.delaunay_triples/triangulate.regular_grid.

Such an implementation has some limitations:

• The internal _triangulate function is complicated because it needs to deal with both table and grid outputs.
• We have to maintain similar docstrings in three functions (although the private _triangulate function doesn't have to have docstrings)
• In triangulate.delaunay_triples/triangulate.regular_grid, we have to call the private function like:

            return triangulate._triangulate(
                data=data,
                x=x,
                y=y,
                z=z,
                output_type=output_type,
                outgrid=outgrid,
                spacing=spacing,
                projection=projection,
                region=region,
                verbose=verbose,
                binary=binary,
                nodata=nodata,
                find=find,
                coltypes=coltypes,
                header=header,
                incols=incols,
                registration=registration,
                skiprows=skiprows,
                wrap=wrap,
                **kwargs,
            )

• Aliases are not listed in triangulate.delaunay_triples/triangulate.regular_grid documentation (as reported in No aliases lists given in docs for some functions or methods #2185)

This PR refactors the triangulate wrapper by removing the private _triangulate function. The most obvious benefits of the new implementation are that:

• The triangulate.delaunay_triples method have codes that look like any table-ouput wrappers (e.g., filter1d)
• The triangulate.regular_grid method has codes that look like any grid-output wrappers (e.g., grd2xyz)

Thus, the new implementation is much easier to maintain and also make it easier to refactor in PR #2729.

Preview:

• https://pygmt-dev--3073.org.readthedocs.build/en/3073/api/generated/pygmt.triangulate.html
• https://pygmt-dev--3073.org.readthedocs.build/en/3073/api/generated/pygmt.triangulate.regular_grid.html#pygmt.triangulate.regular_grid
• https://pygmt-dev--3073.org.readthedocs.build/en/3073/api/generated/pygmt.triangulate.delaunay_triples.html#pygmt.triangulate.delaunay_triples

[weiji14]

Looks fine after a quick skim (a little busy this week), and the tests pass, so should be ok.