refactor: migrate AdvancedMarkerElement to native DOM events

[willum070]

Description

As the Maps JavaScript API increasingly adopts Web Components, it's recommended to use native DOM events over the legacy google.maps.event wrapper for elements like AdvancedMarkerElement. This PR updates our samples to align with these modern best practices.

Key Changes

• Native Event Listeners: Replaced all instances of the legacy addListener() method with native addEventListener() across all AdvancedMarkerElements in the repository.
• Click Events: Standardized legacy click event bindings to use the native gmp-click DOM event.
• Drag Events: Migrated the dragend event in advanced-markers-draggable and polyline-utility to use the native gmp-dragend DOM event.
• Cleanup Logic Modernization: Removed the legacy event.clearInstanceListeners() cleanup call in polyline-utility. Because the markers are native DOM nodes that get cleanly discarded (spliced from state and map = null), any attached native gmp- event listeners are naturally garbage collected, rendering explicit cleanup unnecessary.
• Linter Fixes: Removed now-unused event imports from the google.maps.importLibrary('core') destructuring assignments.

Affected Samples (11 total)

• advanced-markers-draggable
• advanced-markers-html
• ai-powered-summaries-basic
• event-closure
• place-nearby-search
• place-text-search
• polyline-utility
• ui-kit-advanced-place-search-nearby
• ui-kit-advanced-place-search-text
• ui-kit-place-search-nearby
• ui-kit-place-search-text

Testing

• Verified successful TypeScript compilation without lint errors (npm start tested successfully).
• Searched the entire codebase to ensure no rogue addListener('click') bindings remain on any Marker elements.

Change-Id: I8977020fc4d94e5edced2a1e17308b19a9cefd5e