screws_tilt_adjust: add option to compute probe-relative points automatically, as well as raise z at the end

[vvuk]

screws_tilt_adjust expects screw points as probe-relative, while bed_screws is nozzle-relative. This is a bit silly (and confusing) -- the system's got the probe offsets, it can do the math faster than I can. In order to maintain backwards compat, this adds a use_bed_screws option to screws_tilt_adjust. If it's set (yes, true, 1), then the screw positions are read from bed_screws, and are offset by the probe offset.

It can't use the ProbePointsHelper's use_xy_offsets, because that may put the points outside of range; it applies the offsets manually, and pushes them within x/y range if they're outside. (It would be nice if ProbePointsHelper had a "and push points in range" option, maybe also a "skip out of range" option.) Also ran into a weird issue that if default_points wasn't specified, ProbePointsHelper suddenly required a points config option; didn't investigate why, from my reading of the code it shouldn't be required.

This patch also adds a end_z option to screws_tilt_adjust to give a z to raise the toolhead to after probing the last point. Otherwise it leaves the toolhead right over top of the last screw you may need to modify; you can manually move and run it again, but if we're trying to be helpful...

(Also -- why do bed_screws and screws_tilt_adjust both exist? They're doing 99% the same work, except one uses a probe and gives you turn instructions, both of which could be optional.. e.g. manual probe, and if you don't know screw info, then it can just give you the relative heights.)

[github-actions]

Thank you for your contribution to Klipper. Unfortunately, a reviewer has not assigned themselves to this GitHub Pull Request. All Pull Requests are reviewed before merging, and a reviewer will need to volunteer. Further information is available at: https://www.klipper3d.org/CONTRIBUTING.html

There are some steps that you can take now:

1. Perform a self-review of your Pull Request by following the steps at: https://www.klipper3d.org/CONTRIBUTING.html#what-to-expect-in-a-review
   If you have completed a self-review, be sure to state the results of that self-review explicitly in the Pull Request comments. A reviewer is more likely to participate if the bulk of a review has already been completed.
2. Consider opening a topic on the Klipper Discourse server to discuss this work. The Discourse server is a good place to discuss development ideas and to engage users interested in testing. Reviewers are more likely to prioritize Pull Requests with an active community of users.
3. Consider helping out reviewers by reviewing other Klipper Pull Requests. Taking the time to perform a careful and detailed review of others work is appreciated. Regular contributors are more likely to prioritize the contributions of other regular contributors.

Unfortunately, if a reviewer does not assign themselves to this GitHub Pull Request then it will be automatically closed. If this happens, then it is a good idea to move further discussion to the Klipper Discourse server. Reviewers can reach out on that forum to let you know if they are interested and when they are available.

Best regards,
~ Your friendly GitIssueBot

PS: I'm just an automated script, not a human being.