FS-7513: round screen size to even numbers to prevent green lines on edge with 1up_top_left+5 and 6x6 layouts

FS-7513: add flag to choose between encoding each frame and using central encoder per codec, add parsing for floor fields and reservation fields in layouts, add param to control bandwidth for consolidated codecs, add  audio-position attr to images in layout to sync with virtual HRTF

FS-7513: refactor conference video muxing to create one distinct encoder per codec used and only create one encoded frame per distinct codec, store current image used by layer on the layer so it is not destroyed before the canvas is written, refactor and rearrange some functions

FS-7513: fix compiler warning about uninitialized var and make sure allocated memory is filled with 0