[Optimization] Add caching for Clarity contracts - ContractContext, source code & ContractAnalysis

[cylewitruk]

Contracts and their properties, source code, analyses, which are otherwise static data once a contract has been installed, are read+deserialized a number of times during the execution of a contract.

Implement a simple, node-global LRU cache for these objects in their deserialized form to optimize access for:

1. Frequently used contracts (pox, bns, costs, etc.),
2. Recently used contracts, to avoid needing to read the data multiple times from disk during a contract execution.

The contracts should be cached (keyed) according to their canonicalized epoch, i.e. a contract canonicalized in both 2.05 and 2.4 would have two entries. So the key would be a tuple of (<qualified contract identifier>, <epoch>).
⚠️ I'm making the assumption that this is possible, particularly when processing cross-epoch transactions? If not, then the contract can be keyed on its identifier alone.

The cache shouldn't be large, just enough to help avoid disk reads and extra deserializations in the short-term. Suggestion at 100 contracts and 100 analyses (which we can make configurable).

ℹ️ The suggested implementation is LruCache from the lru crate. This crate is already used as a transient dependency via rusqlite as part of their query cache, so the dependency graph will not become larger.