Get encoder by name

[gBillal]

In this PR:

• Changed the list_decoders/0 and list_encoders to return map. We'll include more information in this maps (currently added profiles field to encoders).
• profile is not an atom, it should be a binary. To get the available profiles, we should use list_encoders/0.
• We can use any encoder by using a name. (still only video encoders are supported, hardware encoders still needs more config, some of them may work directly without any extra config).

[gBillal]

@mickel8 any feedback will be fixed in the next PR.