fix: Use a separate task provider for shards

[refi64]

Recent VSCode versions warn when a task provider of one type registers tasks of another, leading to issues due to the "crystal" task provider registering "shards" tasks. This fixes that by creating a separate task provider for "shards" tasks.

Ref. #139.

[y8]

@bcardiff can you please take a look at this PR?

Right now running tasks produce error pop-up because of the warning:

The task provider for "crystal" tasks unexpectedly provided a task of type "shards".

It's very distracting :(

Thanks!

[nobodywasishere]

This should be fixed after #168 is merged and tasks are reimplemented.