[7.x] Service specific source maps (backport #5410)

[mergify]

This is an automatic backport of pull request #5410 done by Mergify.
Cherry-pick of 9453fe2 has failed:

On branch mergify/bp/7.x/pr-5410
Your branch is up to date with 'origin/7.x'.

You are currently cherry-picking commit 9453fe24.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   _meta/beat.yml
	modified:   apm-server.docker.yml
	modified:   apm-server.yml
	modified:   beater/beater.go
	modified:   beater/beater_test.go
	modified:   beater/config/config_test.go
	modified:   beater/config/integration.go
	modified:   beater/config/rum.go
	new file:   beater/config/sourcemapping.go
	modified:   model/error_test.go
	modified:   model/sourcemap_test.go
	modified:   model/stacktrace_frame_test.go
	modified:   sourcemap/es_store.go
	new file:   sourcemap/fleet_store.go
	new file:   sourcemap/fleet_store_test.go
	modified:   sourcemap/store.go
	modified:   sourcemap/store_test.go
	modified:   tests/system/test_integration_sourcemap.py

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   apmpackage/apm/manifest.yml
	deleted by us:   changelogs/head.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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[apmmachine]

💚 Build Succeeded

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Build stats

• Build Cause: Pull request #5524 updated

• Start Time: 2021-06-23T11:45:09.945+0000

• Duration: 53 min 26 sec

• Commit: c2bf0b8

Test stats 🧪

Test	Results
Failed	0
Passed	4705
Skipped	120
Total	4825

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