[7.x] [Runtime fields] Editor phase 1 (#81472)

[sebelga]

Backports the following commits to 7.x:

• [Runtime fields] Editor phase 1 ([Runtime fields] Editor phase 1 #81472)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 373780d

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
runtimeFields	-	18	+18

Async chunks

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

id	before	after	diff
indexManagement	1.0MB	1.0MB	+7.0B

Distributable file count

id	before	after	diff
default	43199	43203	+4

Page load bundle

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

id	before	after	diff
indexManagement	586.4KB	586.8KB	+458.0B
runtimeFields	-	24.2KB	+24.2KB
total			+24.7KB

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream