Make block filters case-insensitive

[YaroShkvorets]

There is an issue with using checksummed addresses in block filter query: streamingfast/substreams-foundational-modules#9

I think it makes sense to make block filter case-insensitive. At least I don't see why not.

[sduchesneau]

It could be changed, but first we'll need some version-checking because it is a change that would "silenlty change the output of existing substreams". Not a prio.