Step 4 of N. See earlier commits in the series (via the issue) for the
plan.
This adds the missing methods to policyclient.Client and then uses it
everywhere in ipn/ipnlocal and locks it in with a new dep test.
Still plenty of users of the global syspolicy elsewhere in the tree,
but this is a lot of them.
Updates #16998
Updates #12614
Change-Id: I25b136539ae1eedbcba80124de842970db0ca314
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
1ca4ae598a