[Embeddables][Serialized State Only] Use serialized state in state transfer service

[Heenawter]

Fixes #213153

Summary

This PR ensures that the embeddable state transfer service exclusively uses serialized state. Previously, the transfer service accepted either runtime state or serialized state - but we are in the process of removing the concept of "runtime state" for embeddables (at least as far as the Dashboard is concerned), and this is one step towards that goal.

Note that this PR is built off the subset of "embeddable state transfer service related" changes from #215416 - all I did was clean up these changes, finalized some of the cases that were missed in the original draft, and updated tests as necessary.

Checklist

• Unit or functional tests were updated or added to match the most common scenarios
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

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[Heenawter]

Note that getDashboardPanelFromId also conditionally calls snapshotRuntimeState and throws a PanelNotFound error if unable to find any state for a given ID (either via the Dashboard panel state or via the child API) - the only difference in logic here would be that the serialized state is now spread on top of the panel state. But I think that's... okay? And probably safer?

[elasticmachine]

💔 Build Failed

• Buildkite Build
• Commit: 2d16910

Failed CI Steps

• FTR Configs #99
• FTR Configs #99
• FTR Configs #109
• FTR Configs #109

Test Failures

• [job] [logs] FTR Configs #109 / dashboard app - group 5 dashboard data-shared attributes data-shared-item title can be reset
• [job] [logs] FTR Configs #109 / dashboard app - group 5 dashboard data-shared attributes data-shared-item title can be reset
• [job] [logs] FTR Configs #99 / dashboard panel titles by reference resetting title on a by reference panel sets it to the library title
• [job] [logs] FTR Configs #99 / dashboard panel titles by reference resetting title on a by reference panel sets it to the library title

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
aiops	605	606	+1

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
embeddable	131	132	+1

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
aiops	452.1KB	452.7KB	+651.0B
canvas	1017.1KB	1017.1KB	+28.0B
cases	1.3MB	1.3MB	+13.0B
dashboard	542.9KB	542.8KB	-79.0B
lens	1.4MB	1.4MB	+169.0B
maps	3.0MB	3.0MB	+74.0B
ml	5.4MB	5.4MB	+105.0B
presentationPanel	37.5KB	37.6KB	+63.0B
slo	929.2KB	929.3KB	+42.0B
synthetics	986.3KB	986.3KB	+21.0B
visualizations	342.4KB	342.6KB	+224.0B
total			+1.3KB

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
embeddable	20.6KB	20.6KB	+10.0B

Unknown metric groups

References to deprecated APIs

id	before	after	diff
dashboard	9	7	-2

History

• 💔 Build #287019 failed 3282299
• 💔 Build #286997 failed 94df4e2
• 💔 Build #286764 failed 1dacf31
• 💔 Build #286297 failed 2c252e3

cc @Heenawter

[Heenawter]

Closing this PR in favour of #216232, which is this same work but opened against the "Serialized state only" larger feature branch instead of main.

As a summary of what the problem is - currently, anything passed into the Dashboard via the embeddable transfer service will always be considered the last saved state for that panel. This is fine for creating and passing back new panels, but it causes bad behaviour when editing existing panels:

Screen.Recording.2025-03-27.at.1.53.31.PM.mov

Unfortunately, until we remove runtime state completely and change the way Dashboard handles state, we cannot merge this partial fix into main directly 😭