[glib] (7 commits) ...Merge branch 'param-speedups2' into 'main'

[Philip Withnall <pwithnall src gnome org>]

Summary of changes:

  bdc8b02... param: Add a value_is_valid vfunc (*)
  dacfe8c... param: Add g_param_value_is_valid (*)
  2492565... Add tests for g_param_value_is_valid (*)
  c8e14df... Add another test for g_param_value_is_valid (*)
  b0d1506... gparamspec: Test individual paramspec is_valid() implementa (*)
  c72de9d... gobject: Use value_is_valid (*)
  321fe5d... Merge branch 'param-speedups2' into 'main'

(*) This commit already existed in another branch; no separate mail sent