align verify response with evd get command

[mnsboev]

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Description
This PR refactors the VerificationResponse struct in the evidence verification model to align its field naming and structure with the model used by the jf evd get command. Specifically, the SubjectPath and SubjectChecksum fields are now nested within a new Subject struct, improving consistency across evidence-related commands.
Changes
Refactored VerificationResponse to use a nested Subject struct (Path and Sha256).
Updated all affected test files in jfrog-cli-artifactory/evidence to use the new structure.
Fixed test assertions to match updated output where necessary.