[MEX-698] Remove @Parent decorator from field resolvers

[mad2sm0key]

Reasoning

• associating resolver method arguments (e.g., @parent()) with parameters that were originally passed into the "native" handler has a performance overhead ResolveField performance degradation nestjs/graphql#1770

Proposed Changes

• remove @Parent decorator from field resolve methods where parent is the only argument. This is possible because Nest provides arguments in the original order and parent (root) is always the first one
• remove unnecessary Assets resolver

How to test

• N/A