vim-patch:partial:8.1.0914: code related to findfile() is spread out (#30000)

Problem:    Code related to findfile() is spread out.
Solution:   Put findfile() related code into a new source file. (Yegappan
            Lakshmanan, closes vim/vim#3934)

5fd0f5052f

Keep functions related to wildcard expansion in path.c, as in Vim they
are now spread out among multiple files, which isn't really ideal.

src/nvim/ops.c

@@ -31,6 +31,7 @@
 #include "nvim/ex_cmds_defs.h"
 #include "nvim/ex_getln.h"
 #include "nvim/extmark.h"
+#include "nvim/file_search.h"
 #include "nvim/fold.h"
 #include "nvim/garray.h"
 #include "nvim/garray_defs.h"