Change `_contains` `_starts_with`, `_ends_with` functionality to be case insensitive

[saihaj]

Making contains and starts_with case insensitive is a trivial change in the backend (replacing like with ilike in queries) One small wrinkle is that case-sensitivity is locale-dependent, and the response will depend on the locale in which the database is running, but that's not a new thing, we have that with ordering too. More a reminder that we need to define the locale for all these operations for the network.

Originally posted by @lutter in #1837 (comment)

[saihaj]

@saihaj it seems that we agree - let's keep this as is and introduce a case insensitive filter. We can then monitor usage to try and understand if users are relying on the sensitivity

Originally posted by @azf20 in #3191 (comment)