Move FormatManager back to the media_kit

* We don't aim to replicate this functionality. I don't
think this will be useful at all in future iterations.
Originally I planned to rewrite it on top of the new
BMediaFormat, but now I am of the hopinion this is
greatly unneeded.

media: Remove debug.h, finalize MediaDebug.h

* Funny rust from 0 AD.

Convert more printf to TRACE in media kit.

Media Kit: fix use of pthread_once_init in FormatManager.cpp

Signed-off-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

FormatManager: actually return the singleton instance.

This should work better.

Plugin loading: style fixes.

* Fix style issues pointed by stippi. Thanks!
* Rework the FormatManager instanciation to be thread safe.

Urpdate AddOnManager and FormatManager for Media Kit

* These classes were moved from Media Server, making the use of ports
and messages to communicate with the app irrelevant.
* Split in a separate commit to help git keep track of moved files.

Fixes #4893.

Move media plug-in support to application side.

The media server tried to use node monitoring to dynamically add and
remove plug-ins, but it isn't that useful:
* When a plug-in is added, applications would have to query the media
server to get an up to date list of available formats. For example
MediaConvert populates its format menus on startup.
* When removing a plugin, if an app already had it loaded, there is not
much that can be done to keep it working.
* The list of plugins was not sorted by directories (user vs system
add-ons), so the directories were re-scanned to make sure user add-ons
were returned first, rendering the node monitoring less interesting.

Now, the format handling is done by each application. The node
monitoring is removed, instead the apps will scan the plugin directory
when first using the media kit classes. Restarting the application is
needed to update the media formats list.

Convert more printf to TRACE in media kit.

Media Kit: fix use of pthread_once_init in FormatManager.cpp

Signed-off-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

FormatManager: actually return the singleton instance.

This should work better.

Plugin loading: style fixes.

* Fix style issues pointed by stippi. Thanks!
* Rework the FormatManager instanciation to be thread safe.

Urpdate AddOnManager and FormatManager for Media Kit

* These classes were moved from Media Server, making the use of ports
and messages to communicate with the app irrelevant.
* Split in a separate commit to help git keep track of moved files.

Fixes #4893.

Move media plug-in support to application side.

The media server tried to use node monitoring to dynamically add and
remove plug-ins, but it isn't that useful:
* When a plug-in is added, applications would have to query the media
server to get an up to date list of available formats. For example
MediaConvert populates its format menus on startup.
* When removing a plugin, if an app already had it loaded, there is not
much that can be done to keep it working.
* The list of plugins was not sorted by directories (user vs system
add-ons), so the directories were re-scanned to make sure user add-ons
were returned first, rendering the node monitoring less interesting.

Now, the format handling is done by each application. The node
monitoring is removed, instead the apps will scan the plugin directory
when first using the media kit classes. Restarting the application is
needed to update the media formats list.