Use Java reflection fast paths in Reflector for zero-arg constructors and property getters

[piercifani]

Follow-up to skiptools/skip-foundation#130 and skiptools/skip-android-bridge#33, chasing the same cost: the first kotlin-reflect touch in a process pays the full reflection-infrastructure init (descriptor deserialization, KClassImpl member scans), which lands on the app's main thread during launch.

With those two fixes shipped, the remaining launch-path entry into kotlin-reflect is the generated per-module Bundle_Support.swift:

try! AnyDynamicObject(className: "…._ModuleBundleAccessor_<Module>").moduleBundle!

which reaches Reflector(reflectingClassName:arguments:) (constructor signature matching over KClass.constructors) and Reflector.propertyValue (memberProperties scan) — both kotlin-reflect, for what is in practice a public zero-arg constructor and a plain getter. Any app that touches Bundle.module before first frame (e.g. reading a localized string or a bundled resource in Application.onCreate) pays this.

This PR adds two java.lang.reflect fast paths, falling back to the existing kotlin-reflect paths for everything else:

• Reflector(reflectingClassName:arguments:) with no arguments instantiates via a public zero-arg Java constructor when one exists. Kotlin constructors with default parameters compile to synthetic overloads with a DefaultConstructorMarker parameter, so they don't match and fall through to matchConstructor as before.
• propertyValue first resolves the property's JVM getter (getFoo() / isFoo()) via Class.getMethod and invokes it directly. Java fields (which kotlin-reflect surfaces as properties) have no getter and fall through; non-public Kotlin members are excluded in practice by their module-mangled JVM getter names (getFoo$module). One behavioral nuance: a hypothetical Kotlin member whose getter is JVM-public under a clean name but not KVisibility.PUBLIC would now resolve where the old path threw — I couldn't construct such a case with kotlinc's current name mangling, but flagging it for review.

Measured in the Polymarket app (Pixel 9 emulator, debug build, 12 cold starts, am start -W): median TotalTime 1398ms → 1318ms, and skip.bridge.Reflector frames disappear from the simpleperf startup trace entirely (kotlin-reflect residual drops ~10×, the remainder coming from other libraries).