fix(hooks): skip writing props the consumer never provided

[rpinckne]

Summary

usePropBinding assigns every bound prop as soon as the element exists, including the props the consumer left out, so each custom element receives a burst of undefined writes on mount. Two effects of that on the Maps API:

• it clobbers defaults the element set up for itself (the class of bug [Bug] AdvancedMarker fires "TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node' when "draggable" is true #867 / fix(advanced-marker): only assign anchorLeft/anchorTop when provided #1066 fixed at one call site);
• for deprecated or channel-gated properties it logs a warning the consumer never caused. On the quarterly channel every <Polyline3D> logs autofitsCamera is not supported in this version and The coordinates property is deprecated, and every <Polygon3D> adds innerCoordinates and outerCoordinates, once per element, even when the app only ever passed path and innerPaths.

Change

A prop is written only once it has a value. After that, a later undefined still clears it (removing a prop keeps working), and a fresh object starts untouched even if the hook wrote to a previous one.

This is the general form of the guard #1066 adds inside useAdvancedMarkerAnchoring; it covers every usePropBinding call site in the 3D components, Marker3D, and Popover.

Tests

• src/hooks/__tests__/use-prop-binding.test.tsx: unprovided prop never written (no own property), provided values including null written, value-then-undefined clears, and a new object is left untouched.
• npm test: 23 suites / 194 tests pass, tsc --project tsconfig.test.json, eslint and prettier clean.