refactor(test): move issue #1370 geometry test to cl/_testgo/interface1370

- Move geometry package from _demo to cl/_testdata/geometry1370
- Create simplified test in cl/_testgo/interface1370 following interface test pattern
- Generate .ll file with llgen to verify interface metadata package path fix
- Remove old demo files (issue1370_geometry, issue1370_goast, issue1370_gotypes)
- Remove .tmp-comment files

The new test structure is simpler and follows the existing cl/_testgo/interface pattern,
focusing on demonstrating the interface metadata fix for private methods across packages.

Generated with [codeagent](https://github.com/qbox/codeagent)
Co-authored-by: luoliwoshang <51194195+luoliwoshang@users.noreply.github.com>

cl/_testgo/interface1370/in.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"github.com/goplus/llgo/cl/_testdata/geometry1370"
+)
+
+func main() {
+	rect := geometry1370.NewRectangle(5.0, 3.0)
+	geometry1370.RegisterShape(rect, 42)
+	println("ID:", rect.GetID())
+}