feat: set x-request-id as error trace

[eiri]

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

Please make sure that your PR fulfills the following requirements:

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

PR Type

• [ ] Bugfix
• [x] 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?

What is the new behavior?

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Other information