feat: enabling java function dev experience in vscode + devcontainer

[YunchuWang]

Proposing adding devcontainer files to enable azure java function developers to easily contribute to open source or write java functions by using vscode devcontainer extension in their local boxes.

Step1. Open azure java function worker repo in VsCode
Step2. Install DevContainers extension

Step3. ctrl+shift+p to open command pallete and invoke dev containers command to rebuild and reopen devcontainer

this will build and run a dev container using the config files in root repo of currently opened repo. by default the container mounts the currently opened local dir from host machine which means users can make changes from local VsCode and changes are reflected inside the devcontainer.

Step4. Wait for devcontainer to be running and once ready, you can work on azure java function out of box, with all the tools/extensions/libs installed for you in devcontainer.

Issue describing the changes in this PR

resolves #issue_for_this_pr

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information