Previously, we were always using `**` in the include path. the
effect of this was to always count lines in the entire
repository unless explicitly added to the paths-ignore. This
was incorrect behaviour. Now we only using `**` if the include
path is otherwise empty.

Fixes a bug where we were looking for incorrect keys for metrics rules.
Previously, we were using full language names in the keys. Now, we use
the short language names in the metric ids. This is done through a
simplification of the code.

Also, this change does two smaller things:

1. Prints out the baseline count to the logs
2. Adds the `assertNever` function to ensure we never miss a case in
   a switch statement. This function is borrowed from vscode-codeql.

We were inadvertently using codeql language ids instead of the action's
language ids. There is now a 3-way mapping between the ids used by
the lines counter library, the action, and codeql.

This change passes in a list of file types to the line counting
analysis. These are the languages for the databases being analyzed.
Line count analysis is restricted to these files.

This commit uses a third party library to estimate the lines of code in
a database that is to be analyzed by codeql.

The estimate uses the same includes and excludes globs for determining
which files should be counted.

The lines of code count is returned by language and injected into the
SARIF as `baseline` property in the `${language}/summary/lines-of-code`
metric.