Specify @Priority on producers

[Ladicek]

Fixes #556

[Ladicek]

Submitting as a draft because I need to think a little more about this formulation:

To determine the priority of a producer method or field, the @Priority annotation on the producer method or field is considered first.
If the producer method or field does not declare the @Priority annotation, the @Priority annotation declared on the bean class is used.

The question is: should this be a general principle, or should this only be taken into account during ambiguity resolution? (The CDI specification doesn't use the priority for anything else, but I know of implementations that do use the priority value of beans e.g. for ordering.)

[manovotn]

Submitting as a draft because I need to think a little more about this formulation

Can we swap this from draft to ready for review?
I think the current formulation is precise and would work fine.

[Ladicek]

Yeah, I totally forgot I updated this PR with a more targeted text.