feat(book): [prune] config section

[shekhirin]

Partially #3480, need to also add the --full CLI argument and a separate section about pruning best practices.

[codecov]

Codecov Report

Merging #4328 (5f4ab43) into main (5a7a57d) will decrease coverage by 0.01%.
The diff coverage is 66.66%.

Files Changed	Coverage Δ
bin/reth/src/args/pruning_args.rs	20.00% <ø> (ø)
crates/primitives/src/lib.rs	100.00% <ø> (ø)
crates/primitives/src/prune/mod.rs	36.84% <ø> (ø)
crates/primitives/src/prune/target.rs	59.09% <0.00%> (ø)
crates/prune/src/pruner.rs	78.63% <100.00%> (ø)
crates/storage/provider/src/post_state/mod.rs	95.00% <100.00%> (ø)

... and 9 files with indirect coverage changes

Flag	Coverage Δ
integration-tests	16.80% <0.00%> (-0.02%)	⬇️
unit-tests	63.68% <66.66%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
reth binary	26.11% <ø> (ø)
blockchain tree	82.56% <ø> (ø)
pipeline	90.07% <ø> (ø)
storage (db)	74.77% <100.00%> (ø)
trie	94.88% <ø> (ø)
txpool	47.29% <ø> (ø)
networking	77.47% <ø> (-0.02%)	⬇️
rpc	58.79% <ø> (-0.02%)	⬇️
consensus	63.53% <ø> (ø)
revm	32.01% <ø> (ø)
payload builder	6.78% <ø> (ø)
primitives	86.09% <0.00%> (ø)