Fix 11 non-obsolete warnings

[SpaceManiac]

Pursuant to space-wizards/space-station-14#33279.

Fix:

• Use optimized TryComp for MetaDataComponent and TransformComponent
• Remove unused or never-written private variables
• Remove shadowing nested generics (<T> inside <T>) when the outer <T> is good enough

Silence:

• Duplicate [Dependency] in tests where it's on purpose
• Comparing something == itself in tests where it's on purpose

This doesn't fix any warning with "obsolete" in the name, and doesn't fix this monster:

CSC : warning AD0001: Analyzer 'NUnit.Analyzers.DisposeFieldsInTearDown.DisposeFieldsAndPropertiesInTearDownAnalyzer' threw an exception of type 'System.ArgumentException' with message 'Syntax node is not within syntax tree'. [.../RobustToolbox/Robust.UnitTesting/Robust.UnitTesting.csproj]