test: set case name from initial filename for a sequence

Port more incremental tests.

test/incremental/assert_function.16.zig

@@ -0,0 +1,11 @@
+const hello = "hello".*;
+pub fn main() void {
+    assert(hello[1] == 'e');
+}
+
+pub fn assert(ok: bool) void {
+    if (!ok) unreachable; // assertion failure
+}
+
+// run
+//