feat: UX improvements to Action

[benjackwhite]

Problem

Ended up doing some refactoring in this PR so decided to pull it out

Changes

• Proper loading and not found state for actions
• Smaller action segmented buttons
• Tighter padding on match groups
• Clearer secondary button for adding another match group
• Fixed unloading logic
• Container based re-flowing of the grid (works better with the sidebar)
• Redirect back to the action when undoing delete
• Disable the save button when not changed and hide it when editing unless changed (makes it more obvious how to save it when you make a change)
• Set the default for an match group to be a $pageview
• Re-order options to be Pageview, Autocapture, Other events as that felt more readable

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Does this work well for both Cloud and self-hosted?

How did you test this code?

[github-actions]

Size Change: +4.27 kB (+0.41%)

Total Size: 1.05 MB

Filename	Size	Change
frontend/dist/toolbar.js	1.05 MB	+4.27 kB (+0.41%)

_{compressed-size-action}

[pauldambra]

didn't run it but lgtm

[pauldambra]

i guess we have no visual regression tests for this scene 🙈

[pauldambra]

ran it, looks great...

cypress failure looks real (probably cypress test too tightly bound to vague selector from the look of it)

[daibhin]

Some screenshots of the changes or snapshot stories would be nice to see what's changing here

[posthog-bot]

📸 UI snapshots have been updated

2 snapshot changes in total. 0 added, 2 modified, 0 deleted:

• chromium: 0 added, 2 modified, 0 deleted (diff for shard 1)
• webkit: 0 added, 0 modified, 0 deleted

Triggered by this commit.

👉 Review this PR's diff of snapshots.

[posthog-bot]

📸 UI snapshots have been updated

2 snapshot changes in total. 0 added, 2 modified, 0 deleted:

• chromium: 0 added, 2 modified, 0 deleted (diff for shard 1)
• webkit: 0 added, 0 modified, 0 deleted

Triggered by this commit.

👉 Review this PR's diff of snapshots.