fix: redis run-context handling, error capture, span.outcome

[trentm]

Refs: #2430

Checklist

• Implement code
• Add tests
• Add CHANGELOG.asciidoc entry
• Commit message follows commit guidelines

[apmmachine]

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• Start Time: 2021-11-18T19:50:23.513+0000

• Duration: 22 min 8 sec

• Commit: c2a909a

Test stats 🧪

Test	Results
Failed	0
Passed	22
Skipped	0
Total	22

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[trentm]

REVIEW NOTE: Running this now results in a trace like:

    transaction 4a51a6 "t1"
    `- span 90d434 "SET"
    `- span 71eb7c "GET"
    transaction 30c008 "t2"
    `- span e00acd "SET"
    `- error 0141bc "SET can't be processed. The connection is not yet established and the offline queue is deactivated."

Before this change it would be:

    transaction 4a51a6 "t1"
    `- span 90d434 "SET"
      `- span 71eb7c "GET"
    transaction 30c008 "t2"
    `- span e00acd "SET"

[astorm]

👍