patch 8.2.4036: Vim9: script test file is getting too long

Problem:    Vim9: script test file is getting too long.
Solution:   Split the import/export functionality to a separate file.
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 3c54087..ec12b6b 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -37,6 +37,7 @@
 	test_vim9_expr \
 	test_vim9_fails \
 	test_vim9_func \
+	test_vim9_import \
 	test_vim9_script
 
 TEST_VIM9_RES = \
@@ -47,6 +48,7 @@
 	test_vim9_expr.res \
 	test_vim9_fails.res \
 	test_vim9_func.res \
+	test_vim9_import.res \
 	test_vim9_script.res
 
 # Benchmark scripts.