toaster: Fix stale layer state buttons

toaster: Fix stale layer state buttons

Move the "is available to the project" state computation to the template
for the Layer add/remove buttons, Recipe build/Add layer as done for the
Package add/remove. This is more reliable as we can get an inconsistent
state on the front end JS as there are many opportunities for hitting
out of date project information.

[YOCTO #8294]

Signed-off-by: Michael Wood <michael.g.wood@intel.com>
Signed-off-by: Elliot Smith <elliot.smith@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>