I don't know the relevant programming languages so I don't know what to search for, but generally, if you want to find something in the Firefox source code, supposedly https://searchfox.org is a great way to do that.
There's various well-known tracking parameters that can be stripped, like UTM parameters. Stripping all query parameters would break a lot of sites, like anything in the vein of http://example.com/site.php?id=123
I don't see why they should send the URL somewhere. For Googley reasons, most tracking parameters start with "utm_". You can remove those pretty naïvely, generally without links breaking.