fix: Android Fabric marker content view not measured/laid out

[dacoto]

Summary

Fixes custom marker views rendering incorrectly or not at all when using React Native's New Architecture (Fabric) on Android. In Fabric, contentView was never attached to the view hierarchy, so Fabric skipped measure/layout passes on it and its children entirely.

The fix lazily attaches contentView to the real view hierarchy via super.addView() on the first non-callout child addition. To avoid visually rendering it in the wrong position, translationX is set to -10000f (off-screen); this does not affect createContentBitmap(), which draws in the view's own coordinate space.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Test Plan

• Verify that custom marker views render correctly on Android when using the New Architecture (Fabric).
• Confirm that markers also render correctly with the legacy architecture (Paper) to avoid regressions.
• Check that callout views are unaffected.
• Confirm contentView is not visually rendered at an unexpected position on screen.

Screenshots / Videos

Checklist

• I tested on iOS
• I tested on Android
• I tested on Web
• I updated the documentation (if needed)

[Copilot]

Pull request overview

Fixes Android (React Native New Architecture/Fabric) custom marker views that weren’t being measured/la[id] out because the marker’s contentView was never attached to the native view hierarchy.

Changes:

• Add ensureContentViewAttached() to lazily attach contentView to the view hierarchy.
• Offset the attached contentView off-screen via a large negative translationX.
• Invoke ensureContentViewAttached() when adding non-callout children.

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[dacoto]

Closes #61