Add validation target to avoid losing test coverage with merged test wrappers

[jkoritzinsky]

Add a simple validation target to identify when a project has the same assembly name as another project and produce a build-time error.

Contributes to concerns mentioned in #64841

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Issue Details

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Add a simple validation target to identify when a project has the same assembly name as another project and produce a build-time error.

Contributes to concerns mentioned in #64841

Author:	jkoritzinsky
Assignees:	-
Labels:	area-Infrastructure
Milestone:	-

[BruceForstall]

As long as it works, LGTM (I'm no msbuild guru here...)

[trylek]

Thanks Jeremy for providing the first line of defense. For the generated assembly directives, I suspect this is going to be a longer lead project, among others it will require making sure that the generated names don't escape issue exclusions (i.o.w. migrating issues.targets into ActiveIssue clauses is probably a pre-requisite for this transformation). As a first step, a half-pager design plan for this transformation would be super useful.