Add source report: View sources and show profiling data inline

[brancz]

This is a very exciting moment where a lot of things are coming together. This allows using uploaded source code to be viewed inline with profiling data:

For me personally, this was the only feature I ever still opened the pprof toolchain for, and this is even better than that since it always matches code correctly based on the build ID.

[alwaysmeticulous]

🤖 Meticulous spotted visual differences in 30 of 246 screens tested: view and approve differences detected.

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