feat: introduce at_signing_algo and hashing_algo in at_auth_request and at_onboarding_request

[srieteja]

Closes https://github.com/atsign-foundation/at_libraries/issues/602 - What I did

• Introduce SigningAlgoType and HashingAlgoType in at_auth_request and at_onboarding_request
• Pass signingAlgo and hashingAlgo to at_lookup instance while creation

- How to verify it

• when using an signing or hashing algorithm other than the default should, indicate the same while sending a from verb command to server

- Description for the changelog

feat: introduce at_signing_algo and hashing_algo in at_auth_request and at_onboarding_request

[srieteja]

A functional test has been added but skipped for now. It will be unskipped once https://github.com/atsign-foundation/at_server/issues/2045 has been resolved