(compatible) Improve local precomputed block writing (to individual files)

[Isaac-DeFrain]

Explain your changes:

This PR adds a local precomputed block writing functionality to the daemon. To use it, simply set the new CLI flag --precomputed-blocks-dir PATH when you start the daemon. Block names are consistent with the gcloud naming convention {network}-{height}-{state_hash}.json.

• The new functionality is only triggered when PATH is a Unix directory. Otherwise, a warning will be logged and no block writing happens.

• CLI flags --precomputed-blocks-dir added and --precomputed-blocks-path is changed to --precomputed-blocks-file

• Minor improvements to logging wrt block writing

Explain how you tested your changes:

• I built the mainnet daemon, connected to the network, and confirmed that precomputed blocks were logged to the provided directory as expected.

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[Isaac-DeFrain]

!ci-build-me

[ghost-not-in-the-shell]

!ci-build-me

[Isaac-DeFrain]

Reformatted