* Allow the codeql-action to be run locally

This change allows the codeql-action to be run locally through
[act](https://github.com/nektos/act).

In order to run the action locally, you need to do two things:

1. Add the `CODEQL_LOCAL_RUN: true` environment variable. The only way
   I could figure out how to do this was to add it directly in the
   workflow file in an `env` block. It _should_ be possible to add it
   through a `.env` file and pass it to `act`, but I couldn't get it
   working.
2. Run this command `act -j codeql -s GITHUB_TOKEN=<MY_PAT>`

Setting the `CODEQL_LOCAL_RUN` env var will fill in missing env vars
that the action needs, but isn't set by `act`. It will also avoid
making api calls to github that would fail locally.

This is a refactoring discussed in
https://github.com/github/dsp-codeql/issues/36

…okits and an HTTP client.

…ploaded.