Perform label frustum from LabelGrid.getLabelsToDisplay rather than from Sigma.renderLabels directly

[Yomguithereal]

This means we could avoid linearly checking all the label candidates present from the grid since we know how to filter out some grid cells altogether when they are outside of the viewed rectangle. However it is also possible this does not yield any empirical advantage so we must 1. gather some runtime data before and 2. benchmark.

Note: performing frustum when populating the grid is probably not a good idea because it would require to do it on each render and makes indexation dependent on camera state which is not ideal.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.