Auto merge of #19644 - Xanewok:root-seq-any, r=jdm

Root sequence<any> params using CustomAutoRooter

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

Attempt at https://github.com/servo/servo/issues/16678. At the moment this pulls an external [remove-handle-conv](https://github.com/Xanewok/rust-mozjs/tree/remove-handle-conv) branch for rust-mozjs (removing `FromJSValConvertible` implementation for `HandleValue` and adding one for `*mut JSObject`)

In short, this roots the `sequence<any>` and `sequence<object>` function arguments using `CustomAutoRooter` (introduced in https://github.com/servo/rust-mozjs/pull/382).

As per https://github.com/servo/servo/issues/16678#issuecomment-302224110 the underlying vector contains raw gc thing pointers instead of handles. To do that, this introduces new possible `isMember = "AutoRoot"` value in CodegenRust.py.
The rooted argument is passed to a function wrapped in a `CustomAutoRooterGuard` [RAII root guard](ed5e37a288/src/rust.rs (L586-L588)) (e.g. as `CustomAutoRooterGuard<Vec<JSVal>>`)

I felt quite out of my depth when trying to adapt CodegenRust.py code, so I'd appreciate any help with how can be done better/in a more clean manner.
Also the name `CustomAutoRooterGuard` is quite lengthy, so I'm also open to changing it (`AutoRoot`? `AutoRootGuard`?)

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- [x] These changes fix #16678  (github issue number if applicable).

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Cargo.lock

@@ -1692,7 +1692,7 @@ dependencies = [
  "cssparser 0.23.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "euclid 0.16.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "hashglobe 0.1.0",
- "mozjs 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mozjs 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "servo_arc 0.0.1",
  "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)",
@@ -1862,7 +1862,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "mozjs"
-version = "0.1.9"
+version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cmake 0.1.29 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2586,7 +2586,7 @@ dependencies = [
  "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)",
  "mitochondria 1.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "mozjs 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mozjs 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "msg 0.0.1",
  "net_traits 0.0.1",
  "nonzero 0.0.1",
@@ -3896,7 +3896,7 @@ dependencies = [
 "checksum mio 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)" = "9e965267d4d58496fc4f740e9861118367f13570cadf66316ed2c3f2f14d87c7"
 "checksum miow 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "8c1f2f3b1cf331de6896aabf6e9d55dca90356cc9960cca7eaaf408a355ae919"
 "checksum mitochondria 1.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9de3eca27871df31c33b807f834b94ef7d000956f57aa25c5aed9c5f0aae8f6f"
-"checksum mozjs 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)" = "c9935bada5ea5d70291f21cce7b1bbad507edea12590ebe9cfb6b665fb716480"
+"checksum mozjs 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "2cd8370617e9a151ed9e7b49f38092075d0ae80bdf9f1dcd807a60cc9c3b7151"
 "checksum mozjs_sys 0.50.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ef1e24df9f76502cd4459919098ec1ac3af75ce694ec5b8837aa91f69f2ad0eb"
 "checksum mp3-metadata 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4ab5f1d2693586420208d1200ce5a51cd44726f055b635176188137aff42c7de"
 "checksum mp4parse 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f821e3799bc0fd16d9b861fb02fa7ee1b5fba29f45ad591dade105c48ca9a1a0"