simplify risc0 host

[eyusufatik]

Description

Uses env vars for local / ipc / bonsai prover selection as risc0 intended.

the checks in Risc0BonsaiHost::new is not necessary actually but makes our program fail faster.

Linked Issues

Closes #1381

[codecov]

Codecov Report

Attention: Patch coverage is 63.75000% with 58 lines in your changes missing coverage. Please review.

Project coverage is 77.1%. Comparing base (4a45df5) to head (13c25bf).
Report is 2 commits behind head on nightly.

Files with missing lines	Patch %	Lines
crates/risc0/src/host.rs	72.6%	38 Missing ⚠️
crates/risc0/src/guest.rs	0.0%	18 Missing ⚠️
bin/citrea/src/rollup/bitcoin.rs	0.0%	1 Missing ⚠️
bin/citrea/src/rollup/mock.rs	50.0%	1 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
crates/risc0/src/lib.rs	0.0% <ø> (ø)
bin/citrea/src/rollup/bitcoin.rs	0.0% <0.0%> (ø)
bin/citrea/src/rollup/mock.rs	73.1% <50.0%> (+2.1%)	⬆️
crates/risc0/src/guest.rs	0.0% <0.0%> (ø)
crates/risc0/src/host.rs	72.6% <72.6%> (ø)

... and 4 files with indirect coverage changes

[kpp]

Nice! Then it's not a risc0-bonsai anymore, it's just risc0

[yaziciahmet]

Roll alloy-chains and async-compression back and your lockfile should be fixed.

[yaziciahmet]

LGTM