Depends on github/vscode-codeql#2027 getting merged first.

At the moment we're asking the user to manually right click on
the database folder ('codeql-tutorial-database') and set it as
the current database.

We can take this one step further by defining a command that gets
triggered when we arrive at the step for setting up the database.

The command ("codeQL.setDefaultTourDatabase") will build the URI
pointing to our preloaded database and set it as the current one.

We initially considered whether we can re-use the setCurrentDatabase
command and pass the URI of the database from the codespace itself,
but the URI would be hardcoded as:

file://0-62/workspaces/codespaces-codeql/codeql-tutorial-database

as we can only pass the codeTour extension a command and string
parameters.

This would have been brittle as the filepath for a codespace might
change in the future.

Instead we can define a custom tour command ("setDefaultTourDatabase")
to look at the current workspace folder and build the path to the
database in the CodeQL extension.