[Repo Assist] perf: cache GetParameters/PropertyType/FieldType/EventHandlerType in target-model wrappers

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🤖 This is an automated PR from Repo Assist.

Summary

Caches computed values in the target-model member wrappers (txILConstructorDef, txILMethodDef, txILPropertyDef, txILEventDef, txILFieldDef) inside TargetTypeDefinition to avoid repeated type-resolution and array allocations on every call.

What was happening

Each wrapper function creates a new XxxInfo() object expression. Before this change, several frequently-called members recomputed their results from scratch on every access:

Wrapper	Member	Was doing
txILConstructorDef	GetParameters()	Array.map (txILParameter ...) every call
txILMethodDef	GetParameters()	Array.map (txILParameter ...) every call
txILPropertyDef	PropertyType	txILType resolution every call
txILPropertyDef	GetIndexParameters()	Array.map (txILParameter ...) every call
txILEventDef	EventHandlerType	txILType resolution every call
txILFieldDef	FieldType	txILType resolution every call

Why this matters

TargetTypeDefinition already caches its member wrapper arrays via lazy (ctorDefs, methDefs, fieldDefs, propDefs, eventDefs). This means the same wrapper objects are reused across calls. Without result caching inside the wrappers, every access to GetParameters(), PropertyType, etc. allocates a new array and re-runs IL type resolution — which the F# compiler does repeatedly during type inference against a generative type provider's generated assembly.

Fix

Added lazy bindings before each object expression to cache the computed results:

// txILMethodDef (before)
override __.GetParameters() = inp.Parameters |> Array.map (txILParameter (gps, gps2))

// txILMethodDef (after)
let parametersCache = lazy (inp.Parameters |> Array.map (txILParameter (gps, gps2)))
// ...
override __.GetParameters() = parametersCache.Value
```

Same pattern applied to `txILConstructorDef`, `txILPropertyDef`, `txILEventDef`, and `txILFieldDef`.

Note: This is independent of and complementary to PR #509 (which optimises `Array.filter (canBindXxx)` on the bind-all path).

## Test Status

```
Passed! - Failed: 0, Passed: 157, Skipped: 0, Total: 157

All 157 tests pass.

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