gh-37018: `sage --package properties`
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For example:
```
$ ./sage -package properties --format shell gap ecl
git:sage_package_properties
path_ecl='/Users/mkoeppe/s/sage/sage-rebasing/worktree-
pristine/build/pkgs/ecl'
version_with_patchlevel_ecl='21.2.1'
type_ecl='standard'
source_ecl='normal'
trees_ecl='SAGE_LOCAL'
path_gap='/Users/mkoeppe/s/sage/sage-rebasing/worktree-
pristine/build/pkgs/gap'
version_with_patchlevel_gap='4.12.2'
type_gap='standard'
source_gap='normal'
trees_gap='SAGE_LOCAL'
```
The output is suitable as input for `eval` in Bourne shell. (The default
output format is more human-friendly.)
<!-- Why is this change required? What problem does it solve? -->
Split out from:
- #36740
where this new interface is used to eliminate direct references to
`build/pkgs/` from various scripts and reduce code duplication and
complexity in reading SPKG metadata.
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### :hourglass: Dependencies
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URL: https://github.com/sagemath/sage/pull/37018
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee
