Log when using larger than default pruning cache

[asdacap]

• Warn when using pruning cache larger than 2GB as the pruning hang can take large amount of time which effect attestation.
• Large pruning cache was mainly used to reduce database growth, but since Ahmad's node running 1GB pruning cache for the past 3 month only grow by 25GB, its probably fine to keep the default for most user.
• One scenario where it still make sense is for RPC provider as more cache does improve block processing performance or when setting much longer pruning boundary where large prune cache is unavoidable. For reference, on mainnet minimum prune cache size is about 450MB for past 128 state to support snap serving.

Types of changes

What types of changes does your code introduce?

• Optimization

Testing

Requires testing

• No

If yes, did you write tests?

• Yes
• No

Notes on testing

• Tested with setting and not setting te config.