Bluetooth: ISO: Make setting ISO data explicit

The stack will no longer implicitly set the data path
for ISO channel, and the responsibility for doing that is
now for the upper layers/applications.

This provides additional flexibility for the higher layers
as they can better control the values and timing of the data
path, as well as support removing and even reconfiguring the
data path at will.
This also removes some complexity from the stack.

This commit also fixed a inconsistency in the disconnected
handler. CIS for centrals as well as BIS were still valid
bt_iso_chan channels in the disconnected callback,
but CIS for peripherals were completely cleaned up at this
point. This issue is fixed by moving the disconnected callback
handling to before the code to cleanup the channel for
peripherals.

Since there is a difference in how you remove data paths
depending on the GAP role (central/peripheral), the
iso_info struct type has been expanded to be more
concise of which type of CIS it is.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>