[Turbopack] add feature flag to use the new backend in next.js #36564

Job	Run time
Determine changes	8s
validate-docs-links	10s
optimize-ci / Graphite CI Optimizer	7s
build-native / build	4m 29s
build-next / build	57s
test unit (18) / build	5m 16s
test unit (20) / build	4m 50s
ast-grep lint	15s
test cargo benches	0s
test next-swc wasi	0s
test next-swc wasm	0s
rust check / build	3m 3s
test cargo unit / build	7m 7s
rustdoc check / build	1m 54s
Run devlow benchmarks	0s
test turbopack dev	0s
Test new tests for flakes (dev)	0s
test turbopack production	0s
test turbopack production integration	0s
test turbopack development integration	0s
test dev	0s
test integration	0s
Test new tests for flakes (prod)	0s
test prod	0s
test firefox and safari	0s
test ppr dev	0s
test ppr integration	0s
test ppr prod	0s
types and precompiled / build	56s
lint / build	1m 11s
Test new tests when deployed	0s
report test results to datadog	36s
thank you, next	1s
	31m 0s

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