Currently when data is imported via `consul kv import` it overwrites
keys under the root key. Since `consul kv export` can retrieve data for
the given prefix, i.e. part of the KV tree, importing it under root may
be not what users want.
To mirror prefix behavior from export this PR adds prefix feature to the
import command that adds prefix to all keys that are imported.
Add a skip condition to all tests slower than 100ms.
This change was made using `gotestsum tool slowest` with data from the
last 3 CI runs of master.
See https://github.com/gotestyourself/gotestsum#finding-and-skipping-slow-tests
With this change:
```
$ time go test -count=1 -short ./agent
ok github.com/hashicorp/consul/agent 0.743s
real 0m4.791s
$ time go test -count=1 -short ./agent/consul
ok github.com/hashicorp/consul/agent/consul 4.229s
real 0m8.769s
```
This way we can avoid unnecessary panics which cause other tests not to run.
This doesn't remove all the possibilities for panics causing other tests not to run, it just fixes the TestAgent
