feat(v2.1): use standard zkvm accelerator interface for openvm intrinsics

[shuklaayush]

Combines the standard zkVM accelerator work from the earlier stacked PRs.

• Implements the standard, client-independent zkVM accelerator C interface for OpenVM crypto operations.
• Routes the REVM and Alloy crypto providers through that interface, removing the duplicate provider implementations.
• Simplifies the crate layout to one module and integration test per accelerator, while retaining only the shared BN254/BLS support modules.
• Fixes C output-pointer handling and preserves the EIP-2537 subgroup rules.

Validated with the full accelerator/provider test suite, clippy, and OpenVM RISC-V guest builds.

Reth benchmark: develop-v2.1.0 vs feat/c-interface on block 24846099

Supersedes the earlier stacked PRs:

Closes #686
Closes #687
Closes #689
Closes #690
Closes #691
Closes #692
Closes #693

Resolves INT-8880
Resolves INT-8932
Resolves INT-8933
Resolves INT-8934
Resolves INT-8935
Resolves INT-8939
Resolves INT-8940

[mansur20478]

Looks good, no obvious issues

[Qumeric]

I haven't looked at accelerators themselves, assuming they are correct

revm-crypto LGTM

My LLMs have found no issues