all: cleanup redundant `.ends_with(_test.v)` calls

vlib/v/builder/cc.v

@@ -545,8 +545,7 @@ fn (mut v Builder) cc() {
 			builtin_obj_path := v.rebuild_cached_module(vexe, 'vlib/builtin')
 			libs << builtin_obj_path
 			for ast_file in v.parsed_files {
-				is_test := ast_file.path.ends_with('_test.v') || ast_file.path.ends_with('_test.vv')
-				if is_test && ast_file.mod.name != 'main' {
+				if v.pref.is_test && ast_file.mod.name != 'main' {
 					imp_path := v.find_module_path(ast_file.mod.name, ast_file.path) or {
 						verror('cannot import module "$ast_file.mod.name" (not found)')
 						break

vlib/v/builder/compile.v

@@ -245,7 +245,7 @@ pub fn (v &Builder) get_user_files() []string {
 	if v.pref.is_prof {
 		user_files << os.join_path(preludes_path, 'profiled_program.v')
 	}
-	is_test := dir.ends_with('_test.v') || dir.ends_with('_test.vv')
+	is_test := v.pref.is_test
 	mut is_internal_module_test := false
 	if is_test {
 		tcontent := os.read_file(dir) or {

vlib/v/gen/cgen.v

@@ -215,8 +215,7 @@ pub fn cgen(files []ast.File, table &table.Table, pref &pref.Preferences) string
 		}
 		// println('\ncgen "$g.file.path" nr_stmts=$file.stmts.len')
 		// building_v := true && (g.file.path.contains('/vlib/') || g.file.path.contains('cmd/v'))
-		is_test := g.file.path.ends_with('_test.vv') || g.file.path.ends_with('_test.v')
-		g.is_test = is_test
+		g.is_test = g.pref.is_test
 		if g.file.path == '' || !g.pref.autofree {
 			// cgen test or building V
 			// println('autofree=false')
@@ -1046,7 +1045,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 				// We are using prebuilt modules, we do not need to generate
 				// their functions in main.c.
 				if node.mod != 'main' && node.mod != 'help' && !should_bundle_module
-					&& !g.file.path.ends_with('_test.v')&& node.generic_params.len == 0 {
+					&& !g.pref.is_test&& node.generic_params.len == 0 {
 					skip = true
 				}
 			}

vlib/v/gen/js/js.v

@@ -82,14 +82,14 @@ pub fn gen(files []ast.File, table &table.Table, pref &pref.Preferences) string
 	for file in files {
 		g.file = file
 		g.enter_namespace(g.file.mod.name)
-		g.is_test = g.file.path.ends_with('_test.v') || g.file.path.ends_with('_test.vv')
+		g.is_test = g.pref.is_test
 		g.find_class_methods(file.stmts)
 		g.escape_namespace()
 	}
 	for file in files {
 		g.file = file
 		g.enter_namespace(g.file.mod.name)
-		g.is_test = g.file.path.ends_with('_test.v') || g.file.path.ends_with('_test.vv')
+		g.is_test = g.pref.is_test
 		// store imports
 		mut imports := []string{}
 		for imp in g.file.imports {