gh-36738: `build/bin/sage-spkg`: Add options for checking, cleaning separately from build/install
    
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The `sage-spkg` script installs normal and wheel packages.
We create new options that make it possible to invoke the phases of the
installation separately.
```
   -d: only download the package
   -b: build and install (stage) only, do not run post-install
       or check
   -p: post-install only
   -x: exclusively run the test suite; this may assume that:
        * the package has been installed already and/or that
        * the temporary build directory has not been deleted
   -e: erase (delete) the temporary build directory only
```
This is preparation for improvements in `Makefile.in` in combination
with #36740

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URL: #36738
Reported by: Matthias Köppe
Reviewer(s): Michael Orlitzky

Author: Release Manager