vscode: Add VScode devcontainer environment

Create Open IoT SDK Vscode environment Docker file and
devcontainer.json.
Add custom fast model agent settings file.
Add Docker image build script.
Create bootstrap.sh script for running setup steps:
- install git submodules
- install git pre commits hooks
- generate SDK examples
- install required Python packages
- install Fast Model extension if available

Signed-off-by: Artur Tynecki <artur.tynecki@arm.com>