fix(ngMessage): make ngMessage compatible with ngBind

Fixes #8089
Closes #13074

BREAKING CHANGE:

ngMessage is now compiled with a priority of 1, which means directives
on the same element as ngMessage with a priority lower than 1 will
be applied when ngMessage calls the $transclude function.
Previously, they were applied during the initial compile phase and were
passed the comment element created by the transclusion of ngMessage.
To restore this behavior, custom directives need to have
their priority increased to at least "1".