[MVP] Match Rosetta SDK Spec

[mowkoshka]

🚀 Feature

Mentat should match the Rosetta SDK spec.

Motivation

The goal is to match the Rosetta SDK spec as Mentat is meant to be an SDK for implementing Rosetta services.
This allows us to be added to the rosetta-ecosystem repository and the ecosystem category of the community site.

Implementation

Some of these may already be done or need to be slightly modified.
All bolded ones are required.
Just going to list them all here for now.

• [Feature] Asserter #132
• [Feature] Client #133
• [Epic] Constructor #134
• [Feature] Errors #135
• [Feature] Fetcher #136
• [Feature] Rosetta Keys #137
• [Feature] Parser #138
• [Feature] Reconciler  #139
• [Feature] Server #140
• [Feature] Statefulsyncer #141
• [Feature] Syncer #143
• [Feature] templates #144
• [Feature] Types #145
• [Feature] Utils #146

Additionally, each of these should be demonstrated in an examples directory.