chore: timestamp fork activation semantics

[rkrasiuk]

Description

Snob PR regarding timestamp fork activation semantics.

is_activated means fork activation at a given timestamp (one-time action).
is_active conveys the meaning of fork "activeness" at a given timestamp (continuous property of the fork).

[codecov]

Codecov Report

Merging #4785 (f6d6368) into main (6d634e9) will increase coverage by 0.00%.
Report is 1 commits behind head on main.
The diff coverage is 58.82%.

Files	Coverage Δ
crates/consensus/common/src/validation.rs	73.46% <100.00%> (ø)
crates/primitives/src/chain/spec.rs	98.08% <100.00%> (ø)
crates/revm/src/state_change.rs	73.00% <100.00%> (ø)
crates/rpc/rpc-engine-api/src/engine_api.rs	79.44% <100.00%> (ø)
...torage/provider/src/providers/database/provider.rs	78.90% <100.00%> (ø)
crates/revm/revm-primitives/src/config.rs	91.19% <0.00%> (ø)
crates/transaction-pool/src/validate/eth.rs	6.94% <33.33%> (ø)
crates/payload/basic/src/lib.rs	0.00% <0.00%> (ø)

... and 12 files with indirect coverage changes

Flag	Coverage Δ
integration-tests	16.52% <11.76%> (+<0.01%)	⬆️
unit-tests	63.42% <58.82%> (+<0.01%)	⬆️

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

Components	Coverage Δ
reth binary	32.23% <ø> (ø)
blockchain tree	83.69% <ø> (ø)
pipeline	88.53% <ø> (ø)
storage (db)	73.49% <100.00%> (ø)
trie	94.52% <ø> (+0.03%)	⬆️
txpool	49.97% <33.33%> (ø)
networking	76.87% <ø> (+0.03%)	⬆️
rpc	57.67% <100.00%> (-0.02%)	⬇️
consensus	62.84% <100.00%> (ø)
revm	28.33% <50.00%> (ø)
payload builder	8.20% <0.00%> (ø)
primitives	86.52% <100.00%> (+0.02%)	⬆️

[mattsse]

reasonable