fix: fix writing prover-id to file and reading it

[dprats]

Issue

The CLI wasn't saving autogenerated prover IDs in certain error cases. When reading the prover ID file failed, some error paths didn't properly handle saving the default ID.

Primary changes

• Refactored get_or_generate_prover_id to handle some missing cases (e.g. hitting an error, missing file, etc...)
• Since there are a few cases, refactored the function into smaller functions that are used by the particular case (or re-used as appropriater)
• Simplified error handling to ensure consistent behavior
• Added test coverage for empty file scenarios

Secondary changes

• Moved a print statement so Your current prover identifier is shows up in the Setting up CLI configuration. section (see image below). Before this PR, the prover id was logged in same section as the web socket connection. This was misleading.

[github-actions]

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