[7.x] [ML] Support legacy watcher URL (#86661)

[darnautov]

Backports the following commits to 7.x:

• [ML] Support legacy watcher URL ([ML] Support legacy watcher URL #86661)

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: d41a366

Metrics [docs]

Async chunks

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

id	before	after	diff
ml	7.0MB	7.0MB	+1.7KB
triggersActionsUi	1.6MB	1.5MB	-26.9KB
total			-25.2KB

Distributable file count

id	before	after	diff
default	47486	48249	+763

Page load bundle

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

id	before	after	diff
triggersActionsUi	162.6KB	162.7KB	+102.0B

Unknown metric groups

async chunk count

id	before	after	diff
triggersActionsUi	31	32	+1

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@elasticmachine merge upstream