un-export FastMath functions sin_fast etcetera

[stevengj]

#17302 accidentally exported deprecations for sin_fast(array) etcetera, when these should in fact be in module Base.FastMath. (As a result, the deprecated "vector" methods are exported but the scalar methods are not.)

cc: @Sacha0

[ararslan]

This came up in other submodules as well. See for example #18456.