[google_maps_flutter] Updates min SDK to 3.29 (#9821)

For the `google_maps_flutter` packages:
- Updates the min SDK version to 3.29
- Runs the autoformatter with the new format
- Update code excerpts

This does not update versions because pushing format changes (even in READMEs) isn't worth doing a release that drops an SDK version (which we don't normally version)

Prep for #9816

Author: stuartmorgan-g

packages/google_maps_flutter/google_maps_flutter/CHANGELOG.md

@@ -1,3 +1,7 @@
+## NEXT
+
+* Updates minimum supported SDK version to Flutter 3.29/Dart 3.7.
+
 ## 2.12.3
 
 * Updates the example app to use the zIndexInt param instead of the deprecated zIndex.

packages/google_maps_flutter/google_maps_flutter/README.md

@@ -137,10 +137,11 @@ class MapSampleState extends State<MapSample> {
   );
 
   static const CameraPosition _kLake = CameraPosition(
-      bearing: 192.8334901395799,
-      target: LatLng(37.43296265331129, -122.08832357078792),
-      tilt: 59.440717697143555,
-      zoom: 19.151926040649414);
+    bearing: 192.8334901395799,
+    target: LatLng(37.43296265331129, -122.08832357078792),
+    tilt: 59.440717697143555,
+    zoom: 19.151926040649414,
+  );
 
   @override
   Widget build(BuildContext context) {
@@ -165,6 +166,7 @@ class MapSampleState extends State<MapSample> {
     await controller.animateCamera(CameraUpdate.newCameraPosition(_kLake));
   }
 }
+
 ```
 
 See the `example` directory for a complete sample app.