Add GitHub action which runs static analysis

Now that all of the various issues that static analysis uncovered have
been fixed (#2431, #2432, #2433, #2436, #2437, #2446), I've added a
GitHub action which will run static analysis for every PR going forward.
When static analysis detects issues with your code, the GitHub action
provides a link to download its findings in a form tailored for human
consumption.

Take a look at [this demonstration of what it looks like when static
analysis issues are
found](https://github.com/Svetlitski/jemalloc/actions/runs/5010245602)
on my fork for an example (make sure to follow the instructions in the
error message to download and inspect the results).

.gitignore

@@ -45,6 +45,10 @@
 /src/*.[od]
 /src/*.sym
 
+compile_commands.json
+/static_analysis_raw_results
+/static_analysis_results
+
 /run_tests.out/
 
 /test/test.sh