Update fiddler agent to replace deprecated v2 APIs with faster v3 APIs.

[nikhil-singh-01]

What does this PR do?
This PR rewrites Fiddler's Agent to use new faster v3 APIs. The PR ensures that the results published to DataDog continue to be backwards compatible supporting old metrics names.
Changes:

• Replace v2 APIs - /models, /metrics and /queries with v3 APIs and remove usage of v2/list-projects API.
• Maintain backward compatibility for old metrics names(using v1compat flag) and add another dashboard for newer metric names.
• Add new metric names to metadata.csv
• Update spec.yaml to make FiddlerCheck more configurable.
• Update and add tests for v3 APIs and v1compat flag turned off.

Motivation
What inspired you to submit this pull request?
Functional Reasons:

The existing implementation of Fiddler-Datadog integration uses v2 APIs - list_projects, and v2/queries and metrics
These APIs are deprecated and removed once users are successfully migrated.
These APIs are replaced by v3 APIs which have been in production for 10+ months. These APIs make much more efficient use of caching at every layer, and are faster.

Review checklist

• PR has a meaningful title or PR has the no-changelog label attached
• Feature or bugfix has tests
• Git history is clean
• If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo
• If this PR includes a log pipeline, please add a description describing the remappers and processors.

Additional Notes

Anything else we should know when reviewing?