Add troubleshooting guide for icuc4 setup and socket creation errors

What does this merge request do and why?

This MR adds a troubleshooting guide for icu4c setup and PostgreSQL socket creation failures that were discovered during a pairing session with @jmandell for GDK installation in this issue: #1863 (comment 1438913177).

Related to #1863 (closed)

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.