Upgrade codeql actions to v2

Currently we're using v1, and there have been some important changes since then.

In particular, the latest version, v2.14.4, contains an important security patch:

> The CodeQL CLI no longer supports the `SEMMLE_JAVA_ARGS` environment variable. All previous versions of the CodeQL CLI perform command substitution on the `SEMMLE_JAVA_ARGS` value (for example, replacing `'$(echo foo)'` with `'foo'`) when starting a new Java virtual machine, which, depending on the execution environment, may have security implications. Users are advised to check their environments for possible `SEMMLE_JAVA_ARGS` misuse.

See the [codeql-action release notes](https://github.com/github/codeql-cli-binaries/releases/tag/v2.14.4) for full details.

.github/workflows/codeql-analysis.yml

@@ -42,7 +42,7 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v1
+      uses: github/codeql-action/init@v2
       with:
         languages: ${{ matrix.language }}
         source-root: src
@@ -54,7 +54,7 @@ jobs:
     # 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
+      uses: github/codeql-action/autobuild@v2
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -68,4 +68,4 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v1
+      uses: github/codeql-action/analyze@v2