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

[qweeah]

Happy paths:

• should push a blob from stdin
• should push a blob from a file
• should push a blob from a file and output the descriptor
• progress status should be disabled when --descriptor is provided
• should show preview hint in help doc

Bad paths:

• should fail if no blob file reference is provided
• should fail directly if not logged in

[lizMSFT]

Hi @qweeah , could you also add:

Happy paths:

• should push a blob from a file and output the descriptor with specific media-type (using --media-type)
• should push a blob from a file and output the prettified descriptor
• should skip the push operation if the blob already exists in the target repo

Bad paths:

• should fail if read from input (-) and read password from input (--password-stdin) are both used
• should fail if push a blob from stdin but either blob size (--size) or digest is not provided
• should fail if push a blob from stdin but either blob size (--size) or digest is incorrect
• should fail if push a blob from file but provided blob size (--size) is incorrect
• should fail if push a blob from file but provided blob digest (name[@digest]) is incorrect