[TrustyAI] Add tests for fairness metrics and refactor TrustyAIService

[adolfo-ab]

This PR adds tests for the TrustyAIService fairness metrics, and refactors the main code that interacts with TrustyAIService

Description

Refactors the TrustyAIService utils to make them more generic
Refactors Trusty functions to send inferences, in order to use run_inference_flow
Improve function to check if TrustyAIService registers isvc
Adds new tests for fairness metrics
Migrates drift tests from modelmesh to kserve
Moves create_isvc to utilities/infra.py
Removes utilities/general.py content to infra.py to avoid circular imports

How Has This Been Tested?

Running the code against a working cluster

Merge criteria:

• The commits are squashed in a cohesive manner and have meaningful messages.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[github-actions]

The following are automatically added/executed:

• PR size label.
• Run pre-commit
• Run tox

Available user actions:

• To mark a PR as WIP, add /wip in a comment. To remove it from the PR comment /wip cancel to the PR.
• To block merging of a PR, add /hold in a comment. To un-block merging of PR comment /hold cancel.
• To mark a PR as approved, add /lgtm in a comment. To remove, add /lgtm cancel.
  lgtm label removed on each new commit push.
• To mark PR as verified comment /verified to the PR, to un-verify comment /verified cancel to the PR.
  verified label removed on each new commit push.

Supported labels

{'/wip', '/lgtm', '/hold', '/verified'}

[adolfo-ab]

/verified