This commit modifies the kubernetes operator to use the `tailscale-client-go-v2`
package instead of the internal tailscale client it was previously using. This
now gives us the ability to expand out custom resources and features as they
become available via the API module.
The tailnet reconciler has also been modified to manage clients as tailnets
are created and removed, providing each subsequent reconciler with a single
`ClientProvider` that obtains a tailscale client for the respective tailnet
by name, or the operator's default when presented with a blank string.
Fixes: https://github.com/tailscale/corp/issues/38418
Signed-off-by: David Bond <davidsbond93@gmail.com>
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