feat(x/tx): unknown field filtering

[kocubinski]

Description

Ref: #15170, #15411

A part of #15515, this patch ports unknown field filtering from codec/ to x/tx, a required feature for legacy amino json signing. This implementation uses the proto3 protoreflect API. For reference, the existing unknown field filter.

Please note that a class of error returned from the filter has been removed, namely mismatched type errors, since it was determined this was superfluous given that an unmarshal will fail anyway. This accounts for most for the reduction in LOC between the 2 implementations.

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[amaury1093]

LGTM. I mostly checked that this implementation matches the old one. I didn't dig deep to check for correctness (I'm assuming the old one was correct), plus tests give me good confidence it's correct.

[aaronc]

Tagging x/tx/v0.4.0 with this