Replace checkstyle illegal import rules with RestrictImports

[wendigo]

Alternative approach to https://github.com/airlift/airbase/pull/355 as suggested by @electrum

For reference: https://github.com/skuzzle/restrict-imports-enforcer-rule

[wendigo]

cc @electrum @hashhar @kokosing @findepi

[hashhar]

errorprone profile isn't enabled by default locally so devs won't catch until these reach CI - just something to consider

[wendigo]

@hashhar enforcer is enabled on a default profile. I've checked that PR with the minimal set of flags

[hashhar]

@hashhar enforcer is enabled on a default profile. I've checked that PR with the minimal set of flags

Ah, I was confused between errorprone and enforcer plugins. 😄