Allow disabling built-in CSS classes for FilterSearch component

[k-gerner]

Add a new flag to FilterSearchProps named disableBuiltInClasses.

To address #481
If this property is true, and there are customCssClasses set, then
we will completely remove the builtin CSS classes from the
component.

TEST=manual
Spun up test site and set the property on a component. Saw the
classes get replaced as expected.

[github-actions]

Current unit coverage is 92.08312716476992%
Current visual coverage is 79.01234567901234%
Current combined coverage is 92.58160237388724%

[coveralls]

coverage: 85.327% (-0.05%) from 85.38%
when pulling 708b22e on dev/filter-search-disable-builtin-classes
into 109b443 on main.

[Fondryext]

Don't forget to increment the version. Maybe a new minor version? Could be argued this is kinda like a bugfix though, so I could be fine with a patch. I see an older pull request with Max that hasn't been shipped. May be worth syncing with him real quick to see what the state of that is.

[k-gerner]

I was thinking that I'd just roll up Max's change at the same time and keep the v1.6.7 since that change hadn't been shipped yet, but I think you're actually right that it's more of a minor version change here. I'll update the version to v1.7.0.

(The parent branch of this one will have the wrong name though but that's fine)