Auto merge of #18984 - dsandeephegde:master, r=jdm

Initial steps of Mutation testing

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- Added one strategy of mutation which is replacing occurrences && to ||.
- Added test mapping framework for running mutation tests corresponding to a mutant.
- Added one test_mapping.json to map source file in a folder to WPT test.
- Added README mentioning about Mutation testing.
- Added CI script to invoke mutation test.
---
<!-- 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 #18529 (github issue number if applicable).
- [x] These changes do not require tests because it is a python script to run mutation test and does not change any behavior.

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components/script/dom/test_mapping.json

@@ -0,0 +1,8 @@
+{
+  "xmlhttprequest.rs": [
+    "XMLHttpRequest"
+  ],
+  "range.rs": [
+    "dom/ranges"
+  ]
+}