Fix submap not using all four corners of the input rectangle

[Cadair]

Fixes #4725
Fixes #4734

[kakirastern]

About all set to go, pending like some faster RTD docs build debugging...

[dstansby]

Looks 👍 apart from

• Removing the new test file
• Updating the changelog, stating clearly how users can change code to adapt to this change

[Cadair]

I have upgraded the changelog entry to breaking, mainly to put it towards the top of the changelog for 2.1 so people see it, also added the code to restore behaviour. I have removed the roll test file and update the fixture.

[Cadair]

test fails are real.

[hayesla]

this PR is hurting me brain - good catch on that bug

Does this change what submap returns for cases where wcs axes and pixel axes are perfectly aligned?

[Cadair]

Does this change what submap returns for cases where wcs axes and pixel axes are perfectly aligned?

No in this case the assumption holds and the results will be the same.

[Cadair]

this PR is hurting me brain

Yeha, mine too. Figuring out the regression test really hurt.

[hayesla]

looks good!

That test fail is fair, and probably expected (array size makes more sense now I think..) - the docsting just needs updating

[dstansby]

Woops, sorry for missing the failing test, will mark as needs changes until it's fixed

[Cadair]

I have updated the doctests and found a bug in the process. I was assuming that the frame was HPC. I have now rectified this, added a test for using HGS coords with a map in HPC and HGS and also added a mask test for good measure.

[sunpy-backport]

The backport to 2.0 failed:

Commits ["9ec00247c34dc503ead49f1bae763ebc8ced1b2e","cb23d08ca8e8c1167a651f51e7f4f6fbd517aded","df1324426d4b4f20eebfb342642af611569a58f0","bf7f1b334e8414841e3914837694853b60aca75b","f99faf6855868f3ca84bca9607b2b56d502dd826"] could not be cherry-picked on top of 2.0

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub.
git fetch
# Create new working tree.
git worktree add .worktrees/backport 2.0
# Navigate to the new directory.
cd .worktrees/backport
# Cherry-pick all the commits of this pull request and resolve the likely conflicts.
git cherry-pick 9ec00247c34dc503ead49f1bae763ebc8ced1b2e cb23d08ca8e8c1167a651f51e7f4f6fbd517aded df1324426d4b4f20eebfb342642af611569a58f0 bf7f1b334e8414841e3914837694853b60aca75b f99faf6855868f3ca84bca9607b2b56d502dd826
# Create a new branch with these backported commits.
git checkout -b backport-4727-to-2.0
# Push it to GitHub.
git push --set-upstream origin backport-4727-to-2.0
# Go back to the original working tree.
cd ../..
# Delete the working tree.
git worktree remove .worktrees/backport

Then, create a pull request where the base branch is 2.0 and the compare/head branch is backport-4727-to-2.0.