RadixN: Like Radix4, but supports size 2,3,4,5,6, and 7 cross-FFTs all in the same instance #277

Job	Run time
Check and test Linux arm 64bit with neon (stable)	1m 16s
Check+Test no features (stable)	57s
Check+Test default features (stable)	40s
Check and test Linux arm 64bit with neon (beta)	1m 8s
Check and test WebAssembly with SIMD (stable)	11s
Check+Test no features (beta)	38s
Check+Test default features (beta)	37s
Check and test Linux arm 64bit with neon (nightly)	1m 11s
Check and test WebAssembly with SIMD (beta)	19s
Check+Test no features (nightly)	40s
Check+Test default features (nightly)	39s
Check and test Linux arm 64bit with neon (1.61)	1m 24s
Check and test WebAssembly with SIMD (nightly)	18s
Check+Test no features (1.61)	2m 57s
Check+Test default features (1.61)	2m 51s
Check and test WebAssembly with SIMD (1.61)	15s
Check and test Linux x86 32bit	1m 30s
Rustfmt	13s
	17m 44s

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