verifier: refactor az-snp-vtpm to avoid tss-esapi dep

[shariqahmed-cohere]

az-snp-vtpm depends on tss-esapi to unmarshall TPM quotes which limits its portability to linux. This change replaces that dependency with tpm2-protocol (combined with az-cvm-vtpm) to allow verifier to compile on other platforms.

The new impl leverages existing non-azure SNP functionality along with tpm2-protocol and az-cvm-vtpm. It also adds validity window check on vcek to keep functionality 1-to-1 with the previous az-snp-vtpm flow.

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Note

Medium Risk
Changes attestation verification for Azure SNP vTPM (TPM parsing and SNP/VCEK validation paths); behavior is intended to stay equivalent but any mismatch in TPM or certificate handling would affect trust decisions.

Overview
Refactors Azure SNP vTPM verification so the az-snp-vtpm-verifier feature no longer depends on az-snp-vtpm or tss-esapi (libtss2). TPM quote parsing now uses tpm2-protocol; HCL handling comes from az-cvm-vtpm with default features off so only the HCL path is linked unless tpm-verifier opts into az-cvm-vtpm/verifier.

SNP/VCEK checks are aligned with the existing snp-verifier: sev certificate chains, report signature verification, and shared verify_report_tcb, plus an explicit VCEK not-before/not-after check that chain verification alone did not enforce. Legacy v0 evidence keeps a local Quote type in compat.rs so JSON layout stays unchanged; Azure TDX vTPM keeps its own From<Quote> for TpmQuote so the SNP build path does not pull in libtss2.

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[shariqahmed-cohere]

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