This reverts commit #191 .

* regen

This reverts commit 8a5ba248.

Mostly to pull in iam changes.

Good apidiff signals are lost in the noise of constantly changing
non-stable APIs. Removing it for now: we should think about how to more
holistically test stability between cloud.google.com/go and genproto.

In this CL I've reverted the IAM updates because of a current IAM
problem identified by a colleague. Will pick up IAM changes again after
that's resolved.

BREAKING_CHANGE_ACCEPTABLE: adding grafeas

This allows removal of x/net/sync and x/net/context, which is a welcome
change.

BREAKING_CHANGE_ACCEPTABLE=protoc churn

BREAKING_CHANGE_ACCEPTABLE=adding to interface

BREAKING_CHANGE_ACCEPTABLE=adding methods to interfaces

BREAKING_CHANGE_ACCEPTABLE=redis removed a bunch of and methods fields,
but that's OK because it's an alpha client.

See: https://github.com/google/go-genproto/pull/149

In #149 we removed api-commons-protos from the generation script, since
it is not currently usable. This is the first PR to regenerate with that
change.

BREAKING_CHANGE_ACCEPTABLE=due to b/, annotations are not being synced
to googleapis. Consequentially, several annotation files have been
deleted and various fields/comments have been removed. This largely
shouldn't matter for us, since we're not using microgenerators yet
(which is the only thing that needs annotations).

Currently api-commons-proto is an out-of-date subset of googleapis/googleapis.
This regen script favours api-commons-proto over googleapis/googleapis. These
combined mean that protos get updated in googleapis/googelapis but never get
generated (since we're always favouring the out-of-date api-commons-proto).

This CL removes api-commons-proto from our regen script until it stops being
an out-of-date subset.

See b/123287260. Currently backend.proto and distribution.proto live in
both googleapis/googleapis and googleapis/api-common-protos. The less
up-to-date one is being used (api-common-protos). This commit is created
by pulling down api-common-protos, deleting backend.proto and
distribution.proto, and running the generation scripts with COMMONPROTOS
set to the path of the modified api-commons-proto.

Notable changes include:

- Spanner BatchDML
- New client googleapis/ads/googleads/v1/
- New client googleapis/cloud/asset/v1/
- New client googleapis/cloud/scheduler/v1/

BREAKING_CHANGE_ACCEPTABLE=add ExecuteBatchDml method to interface

- Use go mod tidy to check if deps were added without being added to go.mod.
- Use go mod download to download deps instead of go get.
- Use GO111MODULE=on everywhere applicable.
- Switch to being 1.12 aware.

Updates go.mod to include new version of gRPC, which removes its
dependency on the old github.com/golang/lint in favour of the new
golang.org/x/lint.

Relevant: https://github.com/google/go-genproto/pull/143

BREAKING_CHANGE_ACCEPTABLE=changes to RedisClient interface, which
should not be implemented by any user

apidiff currently fails our build when a breaking change is detected.
This needs tweaking, because sometimes we need to allow breaking
changes:

- An alpha|beta client gets a breaking change. This is acceptable
because breaking changes are expected to alpha|beta clients.
- A gRPC service interface gets a breaking change. This is acceptable
because users are not expected to implement gRPC service interfaces.
- A hard decision was made to allow a breaking change for some reason
like a bug fix.

This PR checks for the commit message to contain a
BREAKING_CHANGE_ACCEPTABLE=<reason>.

Includes new irm/ protos as well as updated speech protos.