gh-36393: `sage --package list`: Sort output, add switches `--{in,ex}clude-dependencies`
We enhance the command `sage --package list`:
- New switches `--{in,ex}clude-dependencies` walk the tree of
dependencies declared in `dependencies` files
- Output is always (uniquified and) sorted, eliminating the use of
`sort` in various scripts
- Handling of `--exclude` is moved to the end, which improves its
applicability.
The new parsing of the `dependencies*` files in `sage_bootstrap` is
generic preparation for handling more of the bootstrapping phase in
Python, as sketched in #33860 (part of #29146).
This PR is immediate preparation for #35593, where it is desired to
create "minimized" lists of system packages that do not include all
standard packages that are really only needed as dependencies of "top-
level" packages.
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes #1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->
<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes #12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->
### :memo: Checklist
<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->
- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation accordingly.
### :hourglass: Dependencies
<!-- List all open PRs that this PR logically depends on
- #12345: short description why this is a dependency
- #34567: ...
-->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
URL: https://github.com/sagemath/sage/pull/36393
Reported by: Matthias Köppe
Reviewer(s): Michael Orlitzky
