[R25] Reject unsupported collection symbols without analyzer crashes

[JetF0x]

Addresses review finding R25.

Collection declarations such as NetworkList<int[]>, NetworkDictionary<int, int[]>, and NetworkList<T> caused AD0001 because the analyzer cast arbitrary element symbols to INamedTypeSymbol. The array declarations could otherwise compile successfully and reach an unsupported runtime codec. Guard the network-object inheritance check with named-symbol matching so unsupported symbol kinds return the existing CN0015 error at the collection property instead of crashing the analyzer.

Add 26 analyzer cases covering arrays, dynamic values, type parameters and constraints, nested array/generic struct fields, dictionary keys, and simultaneous invalid keys and values. Add 14 combined generator/analyzer cases confirming that unsupported array schemas are rejected even when generated C# compiles, and that scalar, string, Guid, network-object, public-field struct, and nullable collections still analyze and emit successfully. The generator test project references the analyzer to run these combined checks.

Validation on .NET SDK 10.0.400 / net8.0:

• Before the production fix, 13 new cases failed with AD0001 and 27 controls passed.
• All 40 focused cases pass with the fix.
• The complete Release solution test run passes all 268 tests: 155 runtime, 79 analyzer, and 34 generator.
• The final focused run after test-source whitespace cleanup passes all 40 cases; the committed diff passes the whitespace check.

The change preserves supported collection types, existing CN0016 key validation, runtime behavior, public APIs, and wire formats. Previously accepted unsupported element symbols now correctly produce an analyzer error. No diagnostics are added or renumbered.