In the doc, we just wait for done.get() to return before closing the
Subscriber.
This commit makes clear that done.get() in the doc is an example
condition.

Updates googleapis#2485.

* fixing broken test - cloud/spanner/SessionPoolIntegrationTest.java

* fixing java style, tests and unused symbol errors.

* fixing missing import

We register a callback to reconnect connection when old connection closes.
When we shut down the subscriber, we close all connections and
begin to shutdown executor.
There is a race: if the callback is called after executor closes,
an exception occurs and we print a scary stack trace.
It doesn't do anything bad; the subscriber is going to go away anyway,
but the stack trace is still confusing.

This commit avoids registering new jobs on executors.
When a connection closes, the callback to determine whether we should
reconnect is called in the RPC thread.

If the connection closes due to some error, the callback should quickly
determine whether we should reconnection. If so, we register the actual
reconnection job on a separate thread. This does not block RPC thread,
and everyone should be happy.

If the connection closes because we're shutting down,
the callback running on RPC thread should determine that we should NOT
reconnect, not register a reconnection job, and we shouldn't see
a stack trace.

Fixes googleapis#2485.

)

Fixes googleapis#2476.

The list of packages created with command:
```shell
find -name '*.java' |
  xargs grep -hr 'package.*\.stub' |
  cut -c 9- |
  sort -u |
  tr ';' ':' |
  tr -d '\n'; echo
```

* refresh dlp client

* refresh with latest dlp_gapic.yaml

Fixes googleapis#2512.

The benchmark executes a series of queries and report
1. how long until we get the fist result back
2. how long we take to iterate through all results.

Fix the link so that it does not 404.
Also change from homepage and example to
product and library docs to match other APIs.

Fixes googleapis#2538.

Schema can be set to null in a response we get from server.
However, we do not allow the user to set to null,
causing confusion.

This commit fixes this by allowing user to set null schema.

Fixes googleapis#2477.

and put the version of netty ssl in one place

Expose the userProject parameter for the List.Buckets operation.
Bump google-api-client dependency to 1.23.0.

Some users were not sure if they could call methods concurrently etc.
This commit points to Guava doc for reference.

* Refreshing auto-generated code for create() -> of() rename
* Updating gax and auth versions

Expose userProject for the operations
- storage.objects.list
- storage.bucket.testIamPermissions
- storage.bucketAccessControls.delete
- storage.bucketAccessControls.get
- storage.bucketAccessControls.insert
- storage.bucketAccessControls.list
- storage.bucketAccessControls.patch
- storage.buckets.getIamPolicy
- storage.buckets.setIamPolicy

Addresses issue googleapis#2494.
Add comments to methods that accept userProject parameter.

If streaming pull connection is idle for a long time,
a firewall/proxy might terminate the connection.
The keepalive should prevent this from happening,
or at least let us notice that the connection is terminated so we don't
wait forever.

Fixes googleapis#2506

…2583)

Some `@see` annotations should instead be `@link`; maven's javadoc plugin fails if `@see` is used incorrectly.