Adds load times to launchpad telemetry context, and adds event for slow loads

[axosoft-ramint]

Some explanation for the current implementation not simply putting the load times on the "on Refreshed" event of the Focus Provider:

1. Having quickpick commands use event listeners feels a bit weird, and I couldn't find an example of any such commands that set up a disposable and listen for events from other services.
2. Because of 1, my current implementation plumbs the load times through the functions that fetch the focus items, which feels weird and causes all these updates to shapes to account for those load times.

If there's a way we can get away with returning just the items on getCategorizedItems and returning the load times separately, I'd love to hear some feedback on that.

[eamodio]

Hey @axosoft-ramint, while reviewing your PR, I'd suggest the following code changes:

👉 Used new util functions

Added new util functions (already on main), and it should now send the slow event anytime it crosses the threshold, but will now capture the full duration even it if errors out

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