Use C++20 std::numbers, std::lerp() (#7696)

* use c++20 concepts and numbers for lmms_constants.h

* replace lmms::numbers::sqrt2 with std::numbers::sqrt2

* replace lmms::numbers::e with std::numbers::e
Also replace the only use of lmms::numbers::inv_e with a local constexpr instead

* remove lmms::numbers::pi_half and lmms::numbers::pi_sqr
They were only used in one or two places each

* replace lmms::numbers::pi with std::numbers::pi

* add #include <numbers> to every file touched so far
This is probably not needed for some of these files. I'll remove those later

* Remove lmms::numbers

Rest in peace lmms::numbers::tau, my beloved

* Add missing #include <numbers>

* replace stray use of F_EPSILON with approximatelyEqual()

* make many constants inline constexpr
A lot of the remaining constants in lmms_constants.h are specific to
SaProcessor. If they are only used there, shouldn't they be in SaProcessor.h?

* ok then, it's allowed to be signed

* remove #include "lmms_constants.h" for files that don't need it
- And also move F_EPSILON into lmms_math.h
- And also add an overload for fast_rand() to specify a higher and lower bound
- And a bunch of other nonsense

* ok then, it's allowed to be inferred

* ok then, it can accept an integral

* fix typo

* appease msvc

* appease msvc again

* Replace linearInterpolate with std::lerp()

As well as time travel to undo several foolish decisions and squash tiny
commits together

* Fix msvc constexpr warnings

* Fix msvc float to double truncation warning

* Apply two suggestions from code review

Co-authored-by: Dalton Messmer <messmer.dalton@gmail.com>

* Apply suggestions from code review

Co-authored-by: Dalton Messmer <messmer.dalton@gmail.com>

* fix silly mistake

* Remove SlicerT's dependence on lmms_math.h

* Allow more type inference on fastRand() and fastPow10f()

* Apply suggestions from code review

Co-authored-by: Dalton Messmer <messmer.dalton@gmail.com>

* Clean up fastRand() a little bit more

---------

Co-authored-by: Dalton Messmer <messmer.dalton@gmail.com>

plugins/DynamicsProcessor/DynamicsProcessor.cpp

@@ -25,8 +25,10 @@
 
 
 #include "DynamicsProcessor.h"
+
+#include <cmath>
+
 #include "lmms_math.h"
-#include "interpolation.h"
 #include "RmsHelper.h"
 
 #include "embed.h"
@@ -189,7 +191,7 @@ Effect::ProcessStatus DynProcEffect::processImpl(SampleFrame* buf, const fpp_t f
 			{
 				float gain;
 				if (lookup < 1) { gain = frac * samples[0]; }
-				else if (lookup < 200) { gain = linearInterpolate(samples[lookup - 1], samples[lookup], frac); }
+				else if (lookup < 200) { gain = std::lerp(samples[lookup - 1], samples[lookup], frac); }
 				else { gain = samples[199]; }
 
 				s[i] *= gain;