Missing source code in the source view

At the moment, the source view is only able to show source code in a small number of cases and only for native code (i.e. code compiled from C/C++/Rust). Over time, we should add support for more cases.

This issue tracks the implementation status of the various cases.

* In profiles from official Firefox builds, captured within Firefox:
* [x] Source code for native code (C/C++/Rust) hosted on hg.mozilla.org
* [x] Source code for native code (C/C++/Rust) hosted on github (Rust standard library)
* [x] Generated sources for native code (C/C++/Rust) stored in an S3 bucket
* [x] Generated sources for macOS arm64 Firefox builds specifically ([bug 1728882](https://bugzilla.mozilla.org/show_bug.cgi?id=1728882))
* [x] Source code for Firefox-internal JavaScript code (`chrome://` etc.) which is hosted on hg.mozilla.org
* [x] Source code for JavaScript code from web pages
* [ ] Source code for WebAssembly code from web pages
* In profiles from local Firefox builds, captured within Firefox:
* [x] Source code for native code (C/C++/Rust) which is stored on the local file system (#3755)
* [x] Source code for Firefox-internal JavaScript code which is stored on the local file system
* [x] Source code for JavaScript code from web pages
* In profiles loaded via `samply`:
* [x] Source code for native code (C/C++/Rust) which is stored on the local file system (#3754)
* [ ] Source code for native code (C/C++/Rust) which is hosted on a debuginfod server (Linux system libraries)
* In uploaded / published profiles, regardless of capturing tool:
* [x] Source code for Rust dependencies which are hosted on crates.io (#3756)
* [ ] Source code which was only stored on the local file system, would need to be uploaded together with the profile (#4018)

The various "native code" cases will be handled first. For anything involving JavaScript, we're still lacking the line number information in many cases (see [bug 1441689](https://bugzilla.mozilla.org/show_bug.cgi?id=1441689)).

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-487)