Fixing relative time range used by RecentMessageLoader.

[dennisoelkers]

Description

Motivation and Context

The RecentMessageLoader component is trying to limit the range of the
search request it used to get the last received message of an input to
the last hour. For this, it uses the range parameter. This is the
correct parameter name for the backend, but the web interface uses a
small conversion helper that expects the parameter to be named
relative for relative time ranges, according to the naming in the old
web interface.

To make the fix as small as possible for a point release, this change
just uses the relative parameter. For master and subsequent releases
we should either switch over to the range parameter or use it in case
the relative parameter is not present. This way we do not discourage
consumers of the UniversalSearchStore to use the actually correct
parameter naming.

Fixes #4510.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• 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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.