e2e: add test specs for `oras blob delete` command

[qweeah]

Happy paths:

• should delete a blob with interactive confirmation, with delete prompt
• should delete a blob with confirmation flag
• should delete a blob with confirmation flag and output descriptor to stdout
• progress status should be disabled when --descriptor is provided should show preview hint in help doc

Bad paths:

• should fail if no blob reference is provided
• should fail if no confirmation flag and descriptor flag is provided
• should fail directly if not logged in

[lizMSFT]

Hi @qweeah , could you also add:

Happy paths:

• should delete a blob with confirmation flag and output prettified descriptor to stdout

Bad paths:

• should fail if the blob reference is not in the form of <name@digest>
• should fail if the specific blob does not exist