[TrimmableTypeMap] Add integration tests for generator-consumed scanner fields

# [TrimmableTypeMap] Add integration tests for generator-consumed scanner fields

Part of https://github.com/dotnet/android/issues/10789

## Context

PR https://github.com/dotnet/android/pull/10827 added integration tests that validate the new `JavaPeerScanner` (SRM-based) against the legacy Cecil-based scanner. These tests cover the fields that **overlap** between the two scanners: `JavaName`, `BaseJavaName`, `ImplementedInterfaces`, `MarshalMethods`, `ActivationCtors`, and type flags (`IsInterface`, `IsAbstract`, `IsGenericDefinition`, `DoNotGenerateAcw`).

However, PR https://github.com/dotnet/android/pull/10808 introduced the Generator pipeline (`ModelBuilder` → `TypeMapAssemblyEmitter`) which consumes several `JavaPeerInfo` fields that are **new concepts with no legacy equivalent**. These fields cannot be validated via legacy-vs-new comparison and need standalone correctness tests.

## Fields not covered by integration tests

| Field | Used by | Risk if wrong |
|---|---|---|
| `IsUnconditional` | `ModelBuilder.IsUnconditionalEntry()` — determines 2-arg (unconditional) vs 3-arg (trimmable) TypeMap attribute | Wrong trimming behavior — types could be incorrectly trimmed or unnecessarily preserved |
| `InvokerTypeName` | `ModelBuilder.BuildProxyType()` — proxy generation for interfaces/abstract types | Missing invoker = runtime `MissingMethodException` when activating interface wrappers |
| `CompatJniName` | `AcwMapWriter` — backward-compatible ACW name for `acw-map.txt` | Broken debugging, profiling, or tooling that relies on `acw-map.txt` |
| `MarshalMethods.ManagedMethodName` | Future UCO wrapper generation | Low risk now, but incorrect values would cause wrong method dispatch |

## Proposed tests

### 1. `IsUnconditional_ComponentTypes`
Scan `UserTypesFixture.dll`:
- Types with `[Activity]`, `[Service]`, `[BroadcastReceiver]`, `[ContentProvider]` → `IsUnconditional = true`
- Plain Java peer types without component attributes → `IsUnconditional = false`
- Types referenced by `[Application(BackupAgent=typeof(X))]` → forced unconditional via cross-reference

### 2. `IsUnconditional_MonoAndroid`
Scan `Mono.Android.dll`:
- All MCW binding types have `DoNotGenerateAcw=true` and should **not** be marked unconditional
- Sanity check: count of unconditional types = 0

### 3. `InvokerTypeName_InterfacesAndAbstractTypes`
Scan `Mono.Android.dll`:
- Every type with `IsInterface = true` should have a non-null `InvokerTypeName`
- The referenced invoker type should actually exist in the scanned assemblies
- Validate resolution via `[Register]` connector (primary) and `{TypeName}Invoker` convention (fallback)

### 4. `InvokerTypeName_UserTypes`
Scan `UserTypesFixture.dll`:
- Concrete user types → `InvokerTypeName = null`
- User-defined interfaces (if present) → invoker resolved correctly

### 5. `CompatJniName_UserTypes`
Scan `UserTypesFixture.dll`:
- Verify `CompatJniName` uses lowercased raw namespace format
- E.g., `MyApp.Namespace.MyType` → `myapp.namespace/MyType`

### 6. `ManagedMethodName_MarshalMethods`
Scan `Mono.Android.dll`:
- Every `MarshalMethodInfo` has non-null, non-empty `ManagedMethodName`
- Spot-check known types (e.g., `Android.App.Activity` has `OnCreate` method)

## Notes

- These tests should live in `tests/Microsoft.Android.Sdk.TrimmableTypeMap.IntegrationTests/`
- Unlike the existing comparison tests, these are **standalone correctness tests** — they validate the new scanner's output against known expectations, not against the legacy scanner
- The `UserTypesFixture` may need additional types (e.g., user-defined interfaces, `[Application]` with `BackupAgent`) to exercise all paths