Chore: Rename `dev` branch to `main`

[lalver1]

This PR implements the first step of code changes needed to transition the benefits repository to tag-based deployments as described in #1527. The code changes are associated with:

• GitHub workflows
• GitHub Issues template
• Terraform
• References to dev in the documentation or code comments

To merge these code changes:

• [x] Rename the dev branch to main in the repository's settings. Renaming instead of creating a new branch avoids having to set up branch protection rules again for main.
• [x] Create the main environment in GitHub’s Environments settings page following the same configuration as the dev environment
  • [x] Set AZURE_WEBAPP_PUBLISH_PROFILE
  • [x] Set AZURE_WEBAPP_NAME
• [x] Merge this PR since GitHub will automatically update the base branch of this PR to main.

Notes

These may be helpful when reviewing workspace.py:

• REASON = Build.Reason: The event that caused the build to run.
• OTHER_SOURCE = System.PullRequest.SourceBranch: The branch that is being reviewed in a pull request.
• INDIVIDUAL_SOURCE = Build.SourceBranchName: The name of the branch in the triggering repo the build was queued for.
• TARGET = System.PullRequest.TargetBranch: The branch that is the target of a pull request.

[github-actions[bot]]

Coverage report

This PR does not seem to contain any modification to coverable code.