resampler: Precompute some common filter coefficients

While this is quite fast on x86 (order of a few microseconds), the
computation can take a few milliseconds on ARM (measured at 1.9ms (32000
-> 48000) and 3.3ms (32000 -> 44100) on a Cortex A53).

Let's precompute some common rates so that we can avoid this overhead on
each stream (or any other audioconvert) instantiation. The approach
taken here is to write a little program to create the resampler
instance, and run that on the host at compile-time to generate some
common rate conversions.

meson_options.txt

@@ -84,6 +84,10 @@ option('audioconvert',
        description: 'Enable audioconvert spa plugin integration',
        type: 'feature',
        value: 'enabled')
+option('resampler-precomp-tuples',
+	description: 'Array of "inrate,outrate[,quality]" tuples to precompute resampler coefficients for',
+	type: 'array',
+	value: [ '32000,44100', '32000,48000', '48000,44100', '44100,48000' ])
 option('bluez5',
        description: 'Enable bluez5 spa plugin integration',
        type: 'feature',