[#825] Remove 'OpSize' modules

Description

Problem: Functionality provided by 'OpSize' modules doesn't seem to match the reference implementation anymore. Additionally, seems like this code isn't actually used anywhere.

Solution: It doesn't make sense to support this code in the future since the only place where it can be potentially used is fee calculation in 'morley-client', which currently uses node RPC responses to estimate operations sizes.

Related issue(s)

Resolves #825 (closed)

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