all: change optional to result of io (#16075)

vlib/v/checker/tests/array_fancy_sort_err.out

@@ -1,6 +1,6 @@
 vlib/v/checker/tests/array_fancy_sort_err.vv:6:8: error: `.sort()` can only use ident, index or selector as argument,
 e.g. `arr.sort(a < b)`, `arr.sort(a.id < b.id)`, `arr.sort(a[0] < b[0])`
-    4 |     text := os.read_file(os.args[0])?
+    4 |     text := os.read_file(os.args[0])!
     5 |     mut lines := text.split_into_lines()
     6 |     lines.sort(a.split('/').last() < b.split('/').last())
       |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

vlib/v/checker/tests/array_fancy_sort_err.vv

@@ -1,7 +1,7 @@
 import os
 
 fn main() {
-	text := os.read_file(os.args[0])?
+	text := os.read_file(os.args[0])!
 	mut lines := text.split_into_lines()
 	lines.sort(a.split('/').last() < b.split('/').last())
 	println(lines.join('\n'))

vlib/v/checker/tests/fn_call_arg_mismatch_err_c.out

@@ -1,7 +1,7 @@
-vlib/v/checker/tests/fn_call_arg_mismatch_err_c.vv:13:18: error: `os.chdir(files)?` (no value) used as value in argument 1 to `os.ls`
+vlib/v/checker/tests/fn_call_arg_mismatch_err_c.vv:13:18: error: `os.chdir(files)!` (no value) used as value in argument 1 to `os.ls`
    11 |             println(files)
    12 |         } else {
-   13 |             println(os.ls(os.chdir(files)?)?)
+   13 |             println(os.ls(os.chdir(files)!)!)
       |                           ~~~~~~~~~~~~~~~~
    14 |         }
    15 |         println(files)

vlib/v/checker/tests/fn_call_arg_mismatch_err_c.vv

@@ -2,15 +2,15 @@ module main
 
 import os
 
-fn list_files() ?[][]string {
-	mut unchecked_files := os.ls('utilities/modules')?
+fn list_files() ![][]string {
+	mut unchecked_files := os.ls('utilities/modules')!
 	println(unchecked_files)
 	for files in unchecked_files {
 		println(files)
 		if os.is_file(files) == true {
 			println(files)
 		} else {
-			println(os.ls(os.chdir(files)?)?)
+			println(os.ls(os.chdir(files)!)!)
 		}
 		println(files)
 	}

vlib/v/checker/tests/for_in_index_optional.out

@@ -1,4 +1,4 @@
-vlib/v/checker/tests/for_in_index_optional.vv:3:18: error: for in: cannot index `?[]string`
+vlib/v/checker/tests/for_in_index_optional.vv:3:18: error: for in: cannot index `![]string`
     1 | import os
     2 | fn main() {
     3 |   for file in os.ls('.') {

vlib/v/checker/tests/optional_type_call_err.out

@@ -1,4 +1,4 @@
-vlib/v/checker/tests/optional_type_call_err.vv:4:5: error: optional type cannot be called directly
+vlib/v/checker/tests/optional_type_call_err.vv:4:5: error: result type cannot be called directly
     2 |
     3 | fn main() {
     4 |     os.ls('.').filter(it.ends_with('.v')) or { return }