Switch `cronet_http` to use jnigen #768

Job	Run time
mono_repo self validate	31s
analyze_and_format; Dart 2.19.0; PKG: pkgs/http_client_conformance_tests; `dart analyze --fatal-i...	28s
analyze_and_format; Dart 3.0.0; PKG: pkgs/http; `dart analyze --fatal-infos`	24s
analyze_and_format; Dart dev; PKGS: pkgs/http, pkgs/http_client_conformance_tests; `dart analyze ...	33s
analyze_and_format; Dart dev; PKGS: pkgs/http, pkgs/http_client_conformance_tests; `dart format -...	22s
unit_test; Dart 3.0.0; PKG: pkgs/http; `dart test --platform chrome`	3m 12s
unit_test; Dart 3.0.0; PKG: pkgs/http; `dart run --define=no_default_http_client=true test/no_def...	34s
unit_test; Dart dev; PKG: pkgs/http; `dart run --define=no_default_http_client=true test/no_defau...	29s
unit_test; Dart 3.0.0; PKG: pkgs/http; `dart test --platform vm`	43s
unit_test; Dart dev; PKG: pkgs/http; `dart test --platform chrome`	3m 0s
unit_test; Dart dev; PKG: pkgs/http; `dart test --platform vm`	44s
	11m 0s

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