Fix Marker position update comparison

[agentpietrucha]

Problem

When rendering list of markers from state array using .map and later updating that state, all markers positions will be updated even though no existing marker has changed its position. In some cases this is causing flickering of the markers' icons. (This is noticeable especially when using MarkerClusterGroup)

Example: https://stackblitz.com/edit/vitejs-vite-lonc2p?file=src%2FMap.tsx (Notice markers' flicker after around 3 secs after the page loads. The most bottom marker will have changed opacity from 1 to 0.5 after 3 secs. I implemented changes from this PR in that example. With those changes there is no more flickering)

Fix

Current check to decide whether or not to update the position is props.position !== prevProps.position, which compares by reference. To update the marker's position only when position value changes, the validation should compare objects by values instead. I added 3 different checks for 3 potential position types: type LatLngExpression = LatLng | LatLngLiteral | LatLngTuple;