Provide support to generate / update bicep content programmatically

**Is your feature request related to a problem? Please describe.**
We want to generate / update bicep content programmatically for a project, which provisions required resources to host the app in Azure. So people does not need to start from scratch. Problem comes when we trying to update the file, since we only want to update necessary part of the bicep file instead of regenerating the whole content: people might customize the content.

**Describe the solution you'd like**
There may be several ways to achieve the goal. One straightforward way is having a parser that converts the content to a syntax tree, so we can operate on it. A language definition file would also be helpful since there're tools that auto generates a language parser for different programming languages(we're using JavaScript). We're also glad if you have other ideas on this.

No files, tests, or entry points are named. Start by reviewing the existing Bicep parsing and language-definition tooling, then determine how programmatic generation and targeted updates could preserve user customizations. Done should include an agreed approach and a usable way to generate or update only the necessary Bicep content.

Written by the indexing model from the issue text.