search: update user search behavior to filter by prefix

[mastercactapus]

Description:
This PR updates user search to follow a prefix-based approach.

Originally search was a simple substring match:
"abc" would match

• "abc"
• "Fooabc"
• "Foo abc"
• "Foo abcBar"

Recently a change was merged that uses a word-based approach:
"abc" would match only

• "abc"
• "Foo abc"

The new form makes sense for many services/policies/schedules as those are usually word-based. Names, however, can vary. This made it difficult as you'd need to type the entire first and/or last name to find a user, as partial matches would not work.

This PR implements a new strategy where each "word" of the search string must at least match a prefix of a "word" in the user's name.
"abc" would match

• "abc"
• "Foo abc"
• "Foo abcBar"

Additionally, you could further restrict your search by adding multiple terms:
"f ab"
Matching both:

• "Foo abc"
• "Foo abcBar"

Which issue(s) this PR fixes:
As part of this, a fix is included to ensure search selects always reflect backend search results
Fixes #919

Out of Scope:
This change does not affect any search functionality beyond users.