Make the memory reporting multi-process aware (#35863)

So far the memory reporter aggregates reports from all processes, and
runs the system reporter only in the main process. Instead it is
desirable to have per-process reports. We do so by:
- creating a ProcessReports struct that holds includes the pid in
addition to the reports themselves.
- running the system memory reporter also in content processes.
- updating the about:memory page to create one report per process, and
add useful information like the pid and the urls loaded in a given
process.

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- [X] `./mach build -d` does not report any errors
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![image](https://github.com/user-attachments/assets/0bafe140-539d-4d6a-8316-639309a22d4a)

Signed-off-by: webbeef <me@webbeef.org>

components/profile/lib.rs

@@ -4,7 +4,8 @@
 
 #![deny(unsafe_code)]
 
-#[allow(unsafe_code)]
 pub mod mem;
+#[allow(unsafe_code)]
+pub mod system_reporter;
 pub mod time;
 pub mod trace_dump;