Validate the name of Filters to avoid the usage of underscore character

Users can use the underscore character on the name of the filter. 

However, Filter search for filters with underscore/dash returns no results, and the related bug JRASERVER-67927 - Filter search for filters with underscore character causes to return no results was closed as "won't fix" with the following note:

While this issue has gathered significant interest, we're unable to implement it. Since version 8.0.0, Jira follows a Unicode standard annex UAX#29 with regards to word boundaries. As per the standard, the underscore character (_) is not considered as a word boundary, which results in the behavior described by this issue.

Because splitting words with underscores would mean creating our own standard, we don't plan to work on this for the foreseeable future. Instead, we encourage you to use characters other than the underscore, e.g. a dash (-) or space, as a workaround.

Suggestion

When the user is creating a filter, we would like to have a validation that would warn the user to not use the underscore character on the name of the filter.