Enable instantiation of multiple branches for repository component

## Describe your feature request

Blueprints enable customers to build/deploy in multiple CodeCatalyst environments (different AWS accounts, regions, etc.). If a blueprint highlights different workflows/configurations for multiple environments (i.e. dev, staging, production, etc.), there is going to be a segment of customers that will partition these deployment environment using Git branches.

## Describe the solution you'd like

In addition to creating a 'main' branch by default with a repository component - I would like to also create additional (optional) branches (i.e. develop) for deployment to other environments. These optional branches would initially just be clones of main.

## Describe alternatives you've considered

An alternative would be using a single blueprint for a single environment (1:1), but having multiple workflows in a single blueprint could take advantage of using a single branch per environment (i.e. main branch == production, develop branch == staging/test, etc.)

Start by locating the repository component implementation and the code path that creates the default main branch. Trace how blueprint environments and repository settings are represented, then define completion as allowing optional additional branches to be created as initial clones of main for deployment environments.

Written by the indexing model from the issue text.