[google_maps_flutter_web] Avoid replacing advanced marker content on move (#11952)

## Description

Avoid replacing an `AdvancedMarkerElement`'s DOM content when a marker update changes only its position. Recreating byte-backed bitmap content produces a new blob-backed image node, which causes the marker to disappear or flicker while moving.

The web implementation now tracks the marker properties that affect rendered content (icon configuration, alpha, visibility, and rotation). Position-only updates preserve the existing DOM node; visual changes still replace it.

Fixes https://github.com/flutter/flutter/issues/188291.

## Tests

- Added web integration coverage for repeated position updates using both `BitmapDescriptor.bytes` and `BytesMapBitmap`.
- Added coverage that visual configuration changes replace the content.
- Ran formatting, analysis, Dart tests, package validation, and publish checks for `google_maps_flutter_web`.
- Ran `advanced_markers_test.dart` through `flutter drive` in Chrome.

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