[desk-tool] Wrap EditorPane and use document id as key to force reload

[bjoerge]

Type of change (check at least one)

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (fix or update to documentation)
• Maintenance
• Other, please describe:

Does this change require a documentation update? (Check one)

• Yes
• No

Current behavior
When switching between documents from the search bar (and with no document list panes open), the portable text editor retains the value from the previous document.

Description
I wasn't able to figure out the root cause, but this PR at least provides a quickfix by changing the key for EditorPane, triggering an unmount + remount with new id.

Note for release

This provides a fix for a bug that affected portable text fields: When switching between documents from the search bar (and with no document list panes open), the portable text editor would retain the value from the previous document.

Checklist

• I have read the Contributing Guidelines
• The PR title includes a link to the relevant issue
• The PR title is appropriately formatted: [some-package] PR title (#123)
• The code is linted
• The test suite is passing
• Corresponding changes to the documentation have been made