refactor gcp cloud tasks scaler

[omerap12]

Provide a description of what has been changed
Refactored the GCP Cloud Tasks scaler and enhanced the unit tests for greater coverage and reliability.

Checklist

• When introducing a new scaler, I agree with the scaling governance policy
• I have verified that my change is according to the deprecations & breaking changes policy
• Tests have been added
• Changelog has been updated and is aligned with our changelog requirements
• A PR is opened to update our Helm chart (repo) (if applicable, ie. when deployment manifests are modified)
• A PR is opened to update the documentation on (repo) (if applicable)
• Commits are signed with Developer Certificate of Origin (DCO - learn more)

Fixes #

Relates to #5797

[zroubalik]

/run-e2e gcp_cloud_tasks
Update: You can check the progress here

[omerap12]

Friendly ping, @zroubalik! :)

[omerap12]

should I merge master branch? @zroubalik @JorTurFer

[JorTurFer]

@wozniakjan