Implement Support for Project Policies

### Current Behavior:
As of v4.6.x, the policy system in Dependency-Track is based around components only. There is no support for policies that operate at the project-level.

### Proposed Behavior:
Expand the policy "engine" to implement support for policies that operate on projects rather than components.
A couple of use cases:
* policy that alerts when project has not had a BOM uploaded for XXX time. See #2052
* policy that allows association between licenses in a project. ie, License X might be acceptable on its' own. Licence Y might be acceptable on its' own. But X and Y must not be allowed in the **same** project because X and Y are mutually incompatible. My employer's legal department is quite insistent about this!