Auto merge of #20391 - modal17:iss19251, r=jdm

Measure cache memory usage

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- [X] make the memory cache data structure derive MallocSizeOf
- [X] add a new IpcReceiver argument to ResourceChannelManager::start that is used for listening to messages from the memory profiler (it must correspond with this sender)
- [X] use run_with_memory_reporting in the network code to register a memory reporter for that thread
- [X] when a message from the memory profiler arrives, create a report that includes that size of the public and private http caches

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [x] These changes fix #19251 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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