Filter active values get lost if field alias start with another's field alias that is configured to be single value

Problem/Motivation

Field alias(es) that start with the same string as as another field alias their filter value gets lost when the other field facet is configured to be single value and has an active value.

How to replicate the bug:

1. create a facet that has an alias like “fieldname”
2. create one with an alias “fieldname1"
3. set the facet “fieldname1” to be single value (the main difference between the dropdown and the links)
4. filter on a “fieldname” value
5. the list got filtered correctly
6. additionally filter on a “fieldname1” value
7. notice that the “fieldname” filter selected value is not selected any more while it should remain

Proposed resolution

Include the separator in the check instead of just checking whether the filter string starts with the field alias.

I'd leave it out of scope to try and fix conflicts with certain values that contain the separator. Or then at least block this issue on #2899277: Configurable separator.

Remaining tasks

test coverage

User interface changes

none

API changes

none

Data model changes

none