Fix permissions issue in dev containers

[dkultasev]

Current version of dev containers throws an error on startup

Running the postCreateCommand from devcontainer.json...

[474780 ms] Start: Run in container: /bin/sh -c whoami && pwd && chmod 777 ./.devcontainer/postCreateCommand.sh && ./.devcontainer/postCreateCommand.sh
vscode
/workspaces/tSQLt
chmod: changing permissions of './.devcontainer/postCreateCommand.sh': Operation not permitted
[478367 ms] postCreateCommand from devcontainer.json failed with exit code 1. Skipping any further user-provided commands.

This PR fixes that issue and also adds vs code tasks to easily re-deploy the db and run the tests