P2-001: KeyInfo parsing dispatch for XMLDSig verify

[polaz]

Summary: implement ROADMAP P2-001 key info parsing dispatch for KeyName, KeyValue, X509Data, and DEREncodedKeyValue.

Scope:

• add parsing types for KeyInfo sources
• parse KeyInfo child elements in order
• ignore unknown child elements in lax mode
• add tests for supported and malformed structures
• wire parsed KeyInfo into verify pipeline for next tasks

Acceptance criteria:

• KeyInfo parsing supports dispatch for KeyName, KeyValue, X509Data, DEREncodedKeyValue
• verify flow remains backward-compatible when KeyInfo is absent
• full workspace checks are green

Dependency follow-up (added):

• attempt to upgrade sha1/sha2 from 0.10 to 0.11 in this issue scope
• upgrade is currently blocked by digest major-version mismatch with rsa/signature path (rsa 0.9 uses digest 0.10)
• complete migration only together with compatible crypto stack update (rsa/signature/ecdsa alignment), then rerun full checks

Estimate: 2d 4h