[DevOps] Merge client deployment actions to CD pipeline

[jji05]

Is your feature request related to a problem? Please describe.

Note

Blocked by #901

To tidy up the repository secrets, it would be best for us to merge the client staging and production deployment scripts into the CD pipeline and enforce the usage of GitHub environments within the deployment scripts.

Describe the solution you'd like

• Remove loose environment variables in Github settings
• Migrate scripts over to correct environments
• Create composite deploy client staging and deploy client production scripts

Acceptance Criteria

• Thoroughly tested
• Same functionality as before

BEFORE MERGING

• Acceptance criteria met
• PR Reviewed (For non-trivial changes)
• Changes tested after rebasing on master or merging in master (hint: git fetch origin master:master, then git rebase master or git merge master)
• All required PR checks passing