feat: Include error cause for Sigstore Internal Errors (#2336)

cc: @mihaimaruseac 

This expands the information the user will receive when there is a
Sigstore Internal Error during the jobs of a BYOB workflow or other
workflows that utilize the `sign-attestations` Github Action. Before,
there was just the assigned error message, but after this, there will be
the error message and cause, if it is an `InternalError`.

Updated sigstore version from `"^1.1.1"` --> `"1.5.1"` to have access to
the class export of `InternalError`.

Signed-off-by: Noah Elzner <[email protected]>

Author: enteraga6