Simplify run triggers

[jlowin]

Summary

Consolidate aggregate run detail triggers into much simpler (and more performant) single triggers

Changes

• Removes run_count and duration columns
• simplifies state trigger logic by:
  • removing a trigger for updating runs with current state info
  • removing a trigger for updating runs with timing details info
  • adding a single, row-level trigger that updates both current state and timing details without any aggregates or comparison functions. This is way simpler than either of the previous two functions
• cleans up default run versions. Previously, runs were created with version 0 and their initial state was also given version 0; this required special casing because all other states are only respected if their version number was greater than the run's current version. This PR bumps the initial state to have version 1, which means special casing is no longer necessary. This does have the affect of incrementing all expected versions, which is why a lot of tests are adjusted in this PR.

Importance

Mirrors https://github.com/PrefectHQ/cloud/pull/2683

Checklist

This PR:

• adds new tests (if appropriate)
• adds a change file in the changes/ directory (if appropriate)

[codecov-commenter]

Codecov Report

Merging #72 into master will decrease coverage by 0.05%.
The diff coverage is 100.00%.