Make drag handles follow cursor more closely

[duranb]

To test:

1. Create a plan and run a simulation to populate multiple rows
2. Verify that upon resizing the drag handle always follow the position of the cursor while respecting min/max sizes.
3. Open the error Console
4. Verify that resizing also follows the cursor in a similar manner.

[AaronPlave]

Much better! Two comments:

1. Could you do this for RowHeaderDragHandleWidth.svelte as well?
2. Seeing the cursor flip between resize and default when dragging row height handles. Looks like that behavior is not from this PR, may be related to the hover+active state styling for home reason not working in this case? And RowHeaderDragHandleWidth is behaving similarly. Any ideas? Could also be addressed in a separate PR, I could take a look too.

[duranb]

Much better! Two comments:

1. Could you do this for RowHeaderDragHandleWidth.svelte as well?
2. Seeing the cursor flip between resize and default when dragging row height handles. Looks like that behavior is not from this PR, may be related to the hover+active state styling for home reason not working in this case? And RowHeaderDragHandleWidth is behaving similarly. Any ideas? Could also be addressed in a separate PR, I could take a look too.

Will do! Oh I see the flickering now too. Is this what you were mentioning before? I thought you were talking about the background color flickering.

[duranb]

@AaronPlave the flickering thing might need to be a separate fix