Make `dcap-qvl` optional in the `attestation` crates (prerequisite for dropping it from the contract WASM)

[pbeza]

Background

Make dcap-qvl (Intel TDX quote verification) an optional dependency of the attestation / mpc-attestation crates, so it is no longer in their default build. dcap-qvl is ~310 KB / ~21% of the mpc-contract WASM, pushing it toward NEAR's 1.5 MiB deployment cap (NEP-509).

This is a prerequisite refactor: it does not move DCAP off-chain or shrink the WASM yet. The end goal is to stop compiling dcap-qvl into the contract, which requires the contract to verify an attestation without linking it — running only the post-DCAP policy checks (measurement allowlist, report-data binding, RTMR replay) and delegating the cryptographic DCAP step to the standalone tee-verifier contract over a cross-contract call. That was impossible before, because DCAP and the policy checks were welded into a single Attestation::verify that always called dcap_qvl::verify::verify, and dcap-qvl was non-optional.

This PR adds that dcap-qvl-free verification path and makes the dependency optional, so the follow-ups become mechanical:

1. Move DCAP off the contract. Instead of running DCAP in-WASM, the contract asks the tee-verifier contract to do it and returns a verified report; the contract then runs only the policy checks via the verify_with_report entry point added in this PR (which needs no dcap-qvl).
2. Drop dcap-qvl from the contract. With DCAP gone from the contract, it stops opting into the new local-verify feature — and dcap-qvl falls out of the build and the WASM.

The follow-up PRs do not exist yet; this is the first slice of a larger integration effort (#3540) being landed as smaller, self-contained PRs.

Acceptance Criteria

• Attestation::verify is split into:
  • verify_with_report(report, …) — post-DCAP policy checks against an already-verified VerifiedReport; does not use dcap-qvl.
  • verify_locally(…) — full DCAP + post-DCAP in one call, behind a new local-verify feature.
• dcap-qvl is optional, gated behind local-verify, so it is absent from the default build of attestation and mpc-attestation (verifiable via cargo tree).
• The dcap_qvl ↔ tee-verifier-interface conversions live in a shared tee-verifier-conversions crate, with the byte-layout pin tests in one place.
• No behavior change: mpc-contract still enables local-verify and verifies locally exactly as before.

Resources & Additional Notes

See the design doc for the full plan.