[Proposal] Ledger struct and related code should live in a single place

[facundoolano]

We currently have a ledger defined in 4 places:

• SnarkOS
• Aleo CLI
• SnarkVM
• snarkos beacon

• SnarkOS beacon is a thin wrapper around the SnarkOS ledger.
• SnarkOS ledger contains a lock to a SnarkVM ledger.
• The Aleo CLI duplicates the one from SnarkOS for the purposes of implementing a local node

This has a few problems:

• Ledger/blockchain knowledge is spread (and partially duplicated) across different repos.
• Adding a new endpoint or changing the interface of a function usually requires making a similar updates in three different repositories and syncing their versions.

A precondition of this change is to have the REST servers consolidated and defined only in SnarkOS as described in #1914 and related issues.

[raychu86]

On the note of consolidated REST servers, the initial "baseline" server was added to snarkVM - https://github.com/AleoHQ/snarkVM/pull/1032. The intention is for snarkOS and other repos requiring a server to utilize the snarkVM server (and add additional routes as needed - https://github.com/AleoHQ/snarkOS/pull/1912)

[ljedrz]

This should now be complete, as the entire Ledger resides in snarkVM