Add a new API to control logging behavior, particularly for implementing
"log once" functionality and periodic logging. This helps avoid spamming
logs with repetitive messages.
The API provides:
- Static and dynamic context creation
- Configurable message identity calculation
- Periodic reset capability
- Context-aware logging macros
- Element message variants with context support
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6855>
Use gst_debug_set_threshold_from_string's new reset behavior to undo
GST_DEBUG and ensure the logging tests have a known configuration.
`gst_debug_set_threshold_from_string ("LOG", TRUE)` has the same effect
as `gst_debug_set_threshold_from_string ("", TRUE)` followed by
`gst_debug_set_default_threshold (GST_LEVEL_LOG)`.
Don't bother remembering the default log level set when the test
started. It will get reset by the next test, anyway.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/605>