feat(ci): Run updates at PR level instead of after merge

[chrismallinson]

Description

Linear ticket: https://linear.app/buildwithfern/issue/FER-6497/ci-handle-seed-generation-and-update-at-pr-level-instead-of-merge
Added new workflow path for updating seed at the PR level instead of waiting for it to merge
Resolves FER-6497

Changes Made

• Added two new flags, create-artifacts and create-pr in auto-update-seed/action.yaml. These are used to pick specific jobs depending on if we are using the legacy workflow (creating PRs after merge to main to update seed) or using the newly added workflow (committing directly to PR)
• Added repository_dispatch trigger to seed.yml, which will be used in later pushes
• Added setup job to update-seed.yml workflow to clean up some code downstream
• Added job to update-seed.yml to commit changes when creating in patch files via auto-update-seed action file
• Added job to trigger snapshot tests after commits are posted (needs further testing, will be used in later commits/PRs)

Testing

Testing with CI, verified:

1. When PR trigger uncommented, seed will run and commit changes to PR that started the job
2. No errors when there are no changes to be committed