[7.x] Add event.outcome to transactions and spans (#4064)

[jalvz]

Backports the following commits to 7.x:

• Add event.outcome to transactions and spans (Add event.outcome to transactions and spans #4064)

[apmmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #4125 updated]

• Start Time: 2020-09-01T09:19:15.969+0000

• Duration: 26 min 27 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3040
Skipped	150
Total	3190

Steps errors

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• Name: Compress

  • Description: tar --exclude=coverage-files.tgz -czf coverage-files.tgz coverage

  • Duration: 0 min 0 sec

  • Start Time: 2020-09-01T09:33:51.537+0000

  • log

• Name: Compress

  • Description: tar --exclude=system-tests-linux-files.tgz -czf system-tests-linux-files.tgz system-tests

  • Duration: 0 min 0 sec

  • Start Time: 2020-09-01T09:45:41.820+0000

  • log

• Name: Test Sync

  • Description: ./script/jenkins/sync.sh

  • Duration: 3 min 39 sec

  • Start Time: 2020-09-01T09:28:37.503+0000

  • log