Site Assembler: ensure only one snackbar notice is shown per unique action

[fushar]

Fixes:

• Assembler - make sure only one snackbar of same type displays at once #77645

Proposed Changes

Currently, each action (add/replace/remove) in the pattern inserter in the Site Assembler flow triggers a snackbar notice in the bottom-right corner of the preview panel on the right. When we do many actions in a short time interval (e.g. trying out headers), this will generate noisy notices and somewhat block the preview.

This PR fixes this problem by only showing one notice per action (add/replace/remove). This is done by assigning the action itself as the ID of the notice, so that we can first remove the previous notice with the same ID before creating a new one.

Testing Instructions

1. Go to /setup/with-theme-assembler/patternAssembler?siteSlug=<site slug>.
2. Try inserting and replacing header/footer many times; make sure that only one Block pattern ... replaced notice is shown.
3. Try inserting and removing homepage patterns many times; make sure that only one Block pattern ... added / Block pattern ... removed` notice is shown (for each add/remove).

Illustrative videos:

Before	After
Screen.Capture.on.2023-06-20.at.15-20-41.mp4	Screen.Capture.on.2023-06-20.at.14-52-01.mp4

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-71003

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-71003&env=jetpack

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~350 bytes removed 📉 [gzipped])

name                    parsed_size           gzip_size
pattern-assembler-step      -1268 B  (-0.1%)     -350 B  (-0.1%)
import-flow                 -1268 B  (-0.1%)     -350 B  (-0.1%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[miksansegundo]

The UX LGTM 👍

Screen.Recording.2566-06-21.at.13.09.09.mov

[arthur791004]

Tested and looks good to me 🎉

[miksansegundo]

@fushar, tested again and looks ready to ship 👍

Screen.Recording.2566-06-22.at.16.20.02.mov

Some friendly reminders:

• we mark all the boxes from the Pre-merge Checklist, even if they are not done but to acknowledge that they are not required.
• after shipped, add it to Marvel Ship Table

[fushar]

@miksansegundo Thanks for testing it again and the reminders 😄 shipping... 🚀