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

Measure cache memory usage

<!-- Please describe your changes on the following line: -->
- [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

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [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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Cargo.lock

@@ -1646,13 +1646,17 @@ dependencies = [
  "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "euclid 0.17.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "hashglobe 0.1.0",
+ "hyper 0.10.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hyper_serde 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "mozjs 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "selectors 0.19.0",
+ "serde 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_bytes 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "servo_arc 0.1.1",
  "smallbitvec 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "time 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "webrender_api 0.57.0 (git+https://github.com/servo/webrender)",
@@ -1888,6 +1892,8 @@ dependencies = [
  "ipc-channel 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "malloc_size_of 0.0.1",
+ "malloc_size_of_derive 0.0.1",
  "matches 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "mime 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "mime_guess 1.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1898,6 +1904,8 @@ dependencies = [
  "serde 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "servo-websocket 0.21.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "servo_allocator 0.0.1",
+ "servo_arc 0.1.1",
  "servo_config 0.0.1",
  "servo_url 0.0.1",
  "threadpool 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1937,6 +1945,7 @@ dependencies = [
  "msg 0.0.1",
  "num-traits 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
+ "servo_arc 0.1.1",
  "servo_config 0.0.1",
  "servo_url 0.0.1",
  "url 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)",