Fix permissions and #! lines for some tests in the upstream build system

d/rules: remove workarounds for script permissions.
The upstream build system now uses the intended permissions throughout.

Retain explicit chmod for *.js, which dh_fixperms assumes should not be executable.

debian/patches/series

@@ -0,0 +1,2 @@
+Sourced-test-snippets-remove-shebang-and-make-non-executa.patch
+Make-corrupt-repo-ref.js-executable.patch