Redundancy in `workspace/diagnostic` partial result type

[ribru17]

Problem

The 3.18 spec defines the partial result type for workspace/diagnostic as follows:

partial result: The first literal send need to be a WorkspaceDiagnosticReport followed by n WorkspaceDiagnosticReportPartialResult literals defined as follows:

Note that WorkspaceDiagnosticReport and WorkspaceDiagnosticReportPartialResult have the exact same object signature, i.e. they serialize to the exact same data. Thus this typing is redundant, likely inherited from how document diagnostic partial results are defined.

Expected behavior

It would make more sense if the spec defined the partial result as the following (for example):

partial result: WorkspaceDiagnosticReportPartialResult[] where WorkspaceDiagnosticReportPartialResult is defined as follows:

Alternatives

Alternatively, the spec can be kept as-is (albeit, with a bit of redundancy) but the metaModel should be changed in a manner similar to the one requested in #2274