Add a blob loader to implement [Blob URL](https://w3c.github.io/FileAPI/#url). The related interfaces to script thread are also declared.
Progressing in parallel with PR #11534. Related to #11131.
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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 part of #10539
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Source-Repo: https://github.com/servo/servo
Source-Revision: 3977128d7e8a21425650894c6ecd55b71bcfa042
