This commit fixes incorrectly built genapply when cross compiling
(#24347) by nuking all fragile CPP logic in it from the orbit. All
target-specific info are now read from DerivedConstants.h at runtime,
see added note for details. Also removes a legacy Makefile and adds
haskell language server support for genapply.

(cherry picked from commit dd4af0e5)
(cherry picked from commit ee800873f62fac8c67cb7034f942a1ed6b72c032)