Update PR template

[Gold856]

Description

All comments are now uncommented to encourage people to actually delete them because they kept getting into commit descriptions and it's annoying. Also tried to make a more convincing argument for collecting test evidence to nudge people into testing and recording the results of that test to help with verifying PR functionality, as what the author has or has not tested is often unclear (and more often than not, edge cases were not tested, which is how #2227 was made.)

This also clarifies that the description should contain info about the events that led to a PR. What event led to that line being added? There happened to be discussion on the FRC Discord about vendordeps compiling against the WPILib kickoff release, which prompted discussion about PV's version locking implemented in #1772, but we couldn't ascertain why #1772 was made (which has since been edited to include that info) given the guarantees given by Gradle and so we had to trudge through Discord to figure out the events triggering that PR, then created #2307 in response (which also contains links and additional context for future readers.)

Finally, the line about settings compatibility has been future-proofed to always require compatibility to the previous season's releases, and to say "all" because of the events leading up to #2331. Seasons end when Champs ends.

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why
• If this PR changes behavior or adds a feature, user documentation is updated
• If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
• If this PR touches configuration, this is backwards compatible with settings back to v2025.3.2
• If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
• If this PR addresses a bug, a regression test for it is added

[samfreund]

Might be good to note that seasons end when champs end in the PR template.

[Gold856]

Done.