move behavior tests from test/stage1/ to test/

And fix test cases to make them pass. This is in preparation for
starting to pass behavior tests with self-hosted.

test/behavior/src.zig

@@ -0,0 +1,17 @@
+const std = @import("std");
+const expect = std.testing.expect;
+
+test "@src" {
+    doTheTest();
+}
+
+fn doTheTest() void {
+    const src = @src();
+
+    expect(src.line == 9);
+    expect(src.column == 17);
+    expect(std.mem.endsWith(u8, src.fn_name, "doTheTest"));
+    expect(std.mem.endsWith(u8, src.file, "src.zig"));
+    expect(src.fn_name[src.fn_name.len] == 0);
+    expect(src.file[src.file.len] == 0);
+}