Use template functions in windows-nat.c

windows-nat.c defines a number of replacement functions that simply
return zero.  This patch removes these in favor of a couple of
template functions.

gdb/ChangeLog
2021-04-30  Tom Tromey  <tromey@adacore.com>

	* windows-nat.c (bad_GetModuleFileNameEx): Remove define.
	(bad_DebugActiveProcessStop, bad_DebugBreakProcess)
	(bad_DebugSetProcessKillOnExit, bad_EnumProcessModules)
	(bad_GetModuleFileNameExW, bad_GetModuleFileNameExA)
	(bad_GetModuleInformation, bad_OpenProcessToken): Remove.
	(bad): New template functions.
	(_initialize_loadable): Update.