Enable CodeQL with codeql-analysis.yml

[andyleejordan]

Adds (almost) automatically setup CodeQL support to resolve #1463. Autobuild didn't work so I just called our Azure pipelines script, and that worked fine.

[andyleejordan]

@rjmholt The "1 analysis not found" is to be expected as CodeQL compares diffs, and there is no pre-existing scan for comparison. All future PRs should work properly, and we can then require that check.

[andyleejordan]

@rjmholt I stepped through these instructions:

And then modified these defaults:

# For most projects, this workflow file will not need changing; you simply need
# to commit it to your repository.
#
# You may wish to alter this file to override the set of languages analyzed,
# or to provide custom queries or build logic.
#
# ******** NOTE ********
# We have attempted to detect the languages in your repository. Please check
# the `language` matrix defined below to confirm you have the correct set of
# supported CodeQL languages.
#
name: "CodeQL"

on:
  push:
    branches: [ master, legacy/1.x ]
  pull_request:
    # The branches below must be a subset of the branches above
    branches: [ master ]
  schedule:
    - cron: '26 18 * * 1'

jobs:
  analyze:
    name: Analyze
    runs-on: ubuntu-latest
    permissions:
      actions: read
      contents: read
      security-events: write

    strategy:
      fail-fast: false
      matrix:
        language: [ 'csharp' ]
        # CodeQL supports [ 'cpp', 'csharp', 'go', 'java', 'javascript', 'python' ]
        # Learn more:
        # https://docs.github.com/en/free-pro-team@latest/github/finding-security-vulnerabilities-and-errors-in-your-code/configuring-code-scanning#changing-the-languages-that-are-analyzed

    steps:
    - name: Checkout repository
      uses: actions/checkout@v2

    # Initializes the CodeQL tools for scanning.
    - name: Initialize CodeQL
      uses: github/codeql-action/init@v1
      with:
        languages: ${{ matrix.language }}
        # If you wish to specify custom queries, you can do so here or in a config file.
        # By default, queries listed here will override any specified in a config file.
        # Prefix the list here with "+" to use these queries and those in the config file.
        # queries: ./path/to/local/query, your-org/your-repo/queries@main

    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
    # If this step fails, then you should remove it and run the build manually (see below)
    - name: Autobuild
      uses: github/codeql-action/autobuild@v1

    # ℹ️ Command-line programs to run using the OS shell.
    # 📚 https://git.io/JvXDl

    # ✏️ If the Autobuild fails above, remove it and uncomment the following three lines
    #    and modify them (or add more) to build your code if your project
    #    uses a compiled language

    #- run: |
    #   make bootstrap
    #   make release

    - name: Perform CodeQL Analysis
      uses: github/codeql-action/analyze@v1

[andyleejordan]

Instructions were found here: https://docs.github.com/en/code-security/secure-coding/setting-up-code-scanning-for-a-repository