Support HTTP proxy for XHR #1954

Job	Run time
build-spidermonkey-win	26m 12s
build-spidermonkey-unix (macos-13, 3.10)	20m 34s
build-spidermonkey-unix (macos-14, 3.10)	11m 3s
build-spidermonkey-unix (ubuntu-22.04-arm, 3.10)	10m 1s
sdist	1s
build-spidermonkey-unix (ubuntu-20.04, 3.10)	1s
check-install-from-sdist	0s
build-and-test	0s
publish-archive	0s
publish	0s
publish-nightly	0s
	1h 7m 52s

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