refactor(attestation/api): Changes to signing key backup service + chalk client side bindings

[MyNameIsMeerkat]

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Issue

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Description

This PR covers a number of changes related to the refactor of the signing key backup service (the artist formerly known, confusingly, as 'secrets manager'). Notably:

• Changed the authentication model of the API to remove the OIDC device code flow from the CLI and instead rely on pre-generated API tokens contained in a chalk profile
• Support for 'refresh' tokens has been removed for the immediate term
• api.nim is no longer needed and was removed
• As a result of the above, two chalk commands login and logout have been removed
• Also removed dependency on QRGen library as that is no longer needed with no device code flow
• A variety of variables and chalk keys have been renamed away from secret manager related names to signing key backup service related names, this should hopefully provide better clarity of code and reduce overuse of 'secret managers' everywhere.
• What was previously referred to as the Chalk API is now refered to as the Chalk Data API to better distinguish it from other APIs
• Notable chalk keys/config vars that have changed are:
  • CHALK_API_KEY -> CHALK_DATA_API_KEY
  • use_secret_manager -> use_signing_key_backup_service
  • secret_manager_url -> signing_key_backup_service_url
  • secret_manager_timeout -> signing_key_backup_service_timeout
• Updated the URL associated with the API endpoint
• Updated endpoint path from /secrets-manager to /signing-key-backup
• Renamed test nosecretmanager.c4m to nosigningkeybackup.c4m

Testing

• rm chalk{.key,.pub} # ensure no chalk.key or chalk.pub files are already present
• chalk load config_file_with_jwt.c4m # load chalk data api token via config & new auth stanza
• chalk --trace setup # gens keys locally, encrypts, & saves them to service
• chalk --trace setup # retrieves saved keys from service, decrypts

[miki725]

sweet I see you are already using retries 🎉