feat: set x-request-id as error trace

[ricellis]

PR summary

If the x-request-id header is on a response use it to set the error trace field (in preference to x-couch-request-id, but still use x-couch-request-id if there is no x-request-id).

Fixes: part of s1037

Note: An existing issue is required before opening a PR.

PR Checklist

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• The commit message follows the
  Angular Commit Message Guidelines.
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• New tests
• Build/CI related changes
• Documentation content changes
• Other (please describe)

What is the current behavior?

The error trace introduced in #719 only handles CouchDB's x-couch-request-id header on responses.

What is the new behavior?

The error trace also handles x-request-id header on responses.

Does this PR introduce a breaking change?

• Yes
• No

Other information