Implement a goal to automate a portion of (root) dependency upgrades

[stuhood]

Updating a root/directly-declared dependency involves:

1. determining the current version (equivalent of a language/field-specific use of ./pants peek)
2. determining available versions (language specific use of a resolver like PEX/pip/Coursier)
3. (optionally) executing either a BUILD file (or language specific file like requirements.txt due to macros) edit to adjust the version

We should look at prior art in other lockfile/version management CLI tools for the rough shape of this goal, but the expected usecases would be either:

1. A user manually updating one or multiple versions locally (./pants update ::)
2. Automation updating a single root dep at a time, á la Create a dependabot-alike for updating thirdparty dependencies for Pants #14193 (./pants update $target)

[kaos]

Related/supercedes #12880

[stuhood]

Related/supercedes #12880

Ah, shoot: I did a poor job of searching. Yea, this one is intended to cover a relatively narrow usecase, which doesn't include add/remove for deps. I would imagine it taking existing target(s) as input, which makes the problem a bit easier maybe.

[cognifloyd]

Related: #15704