Expand dendrite json and Pyandtic v2 Upgrade

[ifrit98]

This updates several things:

• synapse.dict() -> json.loads(synapse.json())
• pydantic to 2.5.2 (latest version) with a massive overhaul
• fastapi to 0.105.0 (latest version)
• updates related synapse code to leverage these upgrades

This effectively increases the types that can be serialized over the bittensor network natively, e.g. datetime

One major bug that this fixes is the limited scope for what kind of objects can be serialized and sent over the wire. For example, datetime objects currently are not serializable because of calling synapse.dict(). The synapse.json() method calls an internal pydantic serialization routine which natively supports datetime objects.

[Eugene-hu]

Looks good, mind expanding a bit about the differences between .dict() vs json.loads? What bug does this fix?

[ifrit98]

Looks good, mind expanding a bit about the differences between .dict() vs json.loads? What bug does this fix?

Yes, will expand in the main comment.