Improve UX for nonexistent profile

[Ekleog-NEAR]

See the discussion at #163.

Basically, there are multiple ways:

1. Never use a nonexistent profile. Basically the behavior before feat: replace the --release flag with a generic --profile flag  #163. Drawback: unintuitive, it’s hard for a user to guess what exactly the options used will be.
2. Have the rust error message in case of nonexistent profile, searchable on google. Basically the behavior after feat: replace the --release flag with a generic --profile flag  #163. Drawback: requires the user to either read the book or make a search on the internet after hitting the issue.
3. Add an always-present warning message explaining how to fix the issue should it arise. Drawback: pollutes the output for people who actually do have the profile setup, which should be the normal path.
4. Parse the rustc output to identify the missing profile message, and add an error message if it is there: Drawback: keeping colors/formatting will probably be hard.
5. Parse Cargo.toml looking for the profile, and add the warning only if the profile is not listed there. Drawback: hard to say how it’d work with workspaces? and basically it’s parsing the same file twice, once by rustc and once by bolero, so behavior mismatches are basically bound to occur.

I tried listing all the ideas for the UX that I could find, can you think of anything else?