Add MA0222 and MA0223 to require the System.Text.Json Respect* options to be configured

[meziantou]

What

Two new rules, one per option, both disabled by default:

Id	Title
MA0222	JsonSourceGenerationOptions should set RespectNullableAnnotations
MA0223	JsonSourceGenerationOptions should set RespectRequiredConstructorParameters

They report a JsonSerializerContext whose [JsonSourceGenerationOptions] attribute does not set the corresponding option, including the contexts that have no attribute at all. A code fixer sets the option to true, adding the attribute when the context has none.

Why

System.Text.Json ignores the nullable annotations of the types it (de)serializes, and treats every constructor parameter as optional. RespectNullableAnnotations and RespectRequiredConstructorParameters (both .NET 9) enable those validations, but default to false for backward compatibility — so a context that never mentions them silently produces instances whose non-nullable members are null, or that were built from an incomplete payload.

Notes for the reviewer

• The rules require the option to be set, not to be set to true. RespectNullableAnnotations = false is a deliberate choice and satisfies MA0222 exactly as = true does. The rules are about making the decision explicit; the fixer is the one that opts for true.
• JsonSerializerDefaults.Strict counts as setting both. It configures them through the constructor, so [JsonSourceGenerationOptions(JsonSerializerDefaults.Strict)] stays clean, and a named argument still wins over it. Web and General do not touch the options and still report. Verified against the real generator that Strict sets both, and that an explicit RespectNullableAnnotations = false overrides it.
• One analyzer reports both rules, following the ValidateFixedAddressValueTypeAttributeUsageAnalyzer (MA0207/MA0208) precedent — the symbol lookups and the JsonSerializerContext walk are shared, so two analyzer types would double the per-compilation cost for the same work. Each rule is still gated on its own property existing on the attribute type, so they can diverge across target frameworks.
• The diagnostic on a context without the attribute skips the partial declaration the source generator emits, so it never points at (or carries an additional location in) a .g.cs.
• Nothing is reported when the target framework predates .NET 9.
• When both rules fire, fix-all needs two iterations — the two fixes touch the same node. The tests assert this explicitly rather than papering over it.

Tests

JsonSourceGenerationOptionsAnalyzerTests drives the real System.Text.Json source generator (UseFrameworkSourceGenerators), without which the JsonSerializerContext snippets would not compile.

Reference assemblies are pinned to Net90 (the minimum version with the options) rather than the default pack, because the newer generators cannot be loaded by the older Roslyn test hosts. The JsonSerializerDefaults.Strict cases need Net100, whose generators require Roslyn 4.14+, so they are behind #if ROSLYN_4_14_OR_GREATER.

• 21/21 pass on roslyn4.14, 5.0, 5.6 and 5.9; 17/17 on roslyn4.8
• Full roslyn5.9 suite: 4042/4042
• Solution builds with 0 warnings, and dotnet run --project src/DocumentationGenerator exits 0 on a re-run