feat(adaptive_size): floating window's optional adaptive size specification

[MrFixThis]

Given the last merged PR (#1556) suggested by @Khrees, the floating window's adaptive size has been fully blocked, making impossible to allow it for those who actually use it.

if M.View.float.enable and not M.View.adaptive_size then
  -- if the floating windows's adaptive size is not desired, then the
  -- float size should be defined in view.float.open_win_config
  return
end

So i propose to check both the floating window and adaptive size configuration to avoid the resizing behavior in floating windows only when the adaptive size is disabled.

[alex-courtis]

Tested OK with a variety of open_win_config and float false.

[alex-courtis]

Please review @Khrees

[Khrees]

Looks good to me.