ext: alsa: Fix fallback paths for setting buffer and period times

Below fallback paths were introduced in https://github.com/GStreamer/gst-plugins-base/commit/9759810d8206b5f1aa199f98599caec3630a1813 if setting period time after buffer time failed :

1. Set period time and then buffer time if it doesn't work
2. Set only buffer time
3. Set only period time

These all were not functioning properly since they were using old copy of snd_pcm_hw_params_t which already had some fields set as per previous try and this was causing issues as driver was referring to that old value while trying to set them again in fallback paths.

So now we always use the initial copy of snd_pcm_hw_params_t for every fallback and same is also being done at pulseaudio/pulseaudio@557c4295

Also we change the sequence to set period time earlier than buffer time since period bytes being the smaller unit, most of the times if underlying alsa device has a dependency then it is of period bytes to be a multiple of some value (as per underlying DMA constraint) and rest of the parameters like buffer bytes need to be adjusted as per period bytes.

The same sequence is also followed in alsa-utils at https://github.com/alsa-project/alsa-utils/commit/9b621eeac4d55c4e881f093be5b163ca07d01b63

Fix 2) and 3) scenarios by returning success if the exclusive setting is passed and not doing any further setting for buffer time or period time.

Add new fallback path of not setting any buffer time and period time if all above fallback paths fail. The same is also being followed at aforementioned pulseaudio commit.

In case of alsasink, remove the retry goto label, since it is not required anymore as fallback paths take care of setting default values if driver is not accepting any of the fallback paths.

Use separate label for exit to free params structs and return err code. This also fixes leak in no_rate goto path in alsasink