Auto merge of #11523 - szeged:random_id, r=jdm

Add random Device ID generation

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The [spec](https://webbluetoothcg.github.io/web-bluetooth/#add-an-allowed-bluetooth-device) (2. step) defines that the device id can't be the public address, therefore we generate a random id.

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

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because there are no webbluetooth test api implementation yet.

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components/net/lib.rs

@@ -35,6 +35,7 @@ extern crate net_traits;
 extern crate openssl;
 extern crate openssl_verify;
 extern crate profile_traits;
+extern crate rand;
 extern crate rustc_serialize;
 extern crate threadpool;
 extern crate time;