Add new filters for case insensitive match `_contains_insensitive` , `_starts_with_insensitive`, `_ends_with_insensitive`

[saihaj]

Reasonable on breaking existing dapps - @lutter @saihaj @dotansimha what do you think about introducing a new i_contains, i_starts_with option in the where, to provide specific case insensitive behaviour? My instinct is that the case-sensitivity is not what most users would expect, but I can't think of an easy way to validate if dapps are relying on it.

We are addressing the database locale issue separately: #3118

Originally posted by @azf20 in #3191 (comment)