fix: update vulnerable Hickory DNS dependencies

[kvinwang]

Summary

• update dcap-qvl to the released 0.5.2 and reqwest to 0.13.4
• keep the asynchronous hickory-dns resolver and consolidate Hickory on 0.26.1
• adapt the Hickory resolver, reqwest TLS, and dcap-qvl collateral client APIs
• remove vulnerable hickory-proto 0.25.2 from Cargo.lock

This addresses Dependabot alert #357 (GHSA-3v94-mw7p-v465).

Validation

• cargo fmt --check --all
• cargo clippy -- -D warnings -D clippy::expect_used -D clippy::unwrap_used --allow unused_variables
• cargo check --workspace --all-targets
• ./run-tests.sh
• verified the lockfile contains only hickory-net, hickory-proto, and hickory-resolver 0.26.1

[Copilot]

Pull request overview

This PR updates Rust dependencies to remediate the Hickory DNS advisory (GHSA-3v94-mw7p-v465) by consolidating Hickory crates on 0.26.1, bumping reqwest to 0.13.4, and upgrading dcap-qvl to 0.5.2, with corresponding API adaptations across the codebase.

Changes:

• Upgrade reqwest to 0.13.4 and adjust TLS/root-certs configuration code for the new API.
• Consolidate hickory-resolver usage on 0.26.1 and update resolver call sites to new types/APIs.
• Upgrade dcap-qvl to 0.5.2 and migrate collateral fetching/verification to CollateralClient.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
dstack/tdx-attest/examples/test_tdx.rs	Switches quote verification to dcap-qvl CollateralClient API.
dstack/ra-rpc/src/client.rs	Updates reqwest TLS/root-cert configuration to reqwest 0.13 APIs.
dstack/ra-rpc/Cargo.toml	Updates reqwest feature flags for the new reqwest version.
dstack/nsm-qvl/Cargo.toml	Updates reqwest feature flags for the new reqwest version.
dstack/gateway/src/proxy/tls_passthough.rs	Migrates DNS TXT resolution to Hickory 0.26.1 resolver/lookup APIs and preserves caching behavior.
dstack/dstack-util/src/host_api.rs	Migrates quote collateral fetch/verify to CollateralClient and normalizes PCCS URL handling.
dstack/dstack-attest/src/attestation.rs	Centralizes PCCS/collateral client creation and migrates TDX verification calls to CollateralClient.
dstack/ct_monitor/Cargo.toml	Updates reqwest feature flags for the new reqwest version.
dstack/certbot/src/acme_client.rs	Migrates ACME DNS TXT self-check to Hickory 0.26.1 resolver/lookup APIs.
dstack/Cargo.toml	Bumps workspace versions for reqwest, dcap-qvl, and hickory-resolver (and reqwest feature set).
dstack/Cargo.lock	Removes vulnerable Hickory versions and locks updated dependency graph (including new transitive crates).

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