Support Couchbase3

[laglangyue]

motivation

relates to #623
support couchbase3
should be after from dropping couchbase2

test

have some test, not finished

docs

not finished

[pjfanning]

thanks - looks like a reasonable approach

there are some issues

• code doesn't compile

[error] /home/runner/work/pekko-connectors/pekko-connectors/couchbase3/src/main/scala/org/apache/pekko/stream/connectors/couchbase3/scaladsl/CouchbaseSource.scala:92:49: too many arguments (found 2, expected 1) for method query: (x$1: com.couchbase.client.java.query.N1qlQuery): rx.Observable[com.couchbase.client.java.query.AsyncN1qlQueryResult]
[error]       .completionStage(cluster.query(statement, options))
[error]                                                 ^
[error] /home/runner/work/pekko-connectors/pekko-connectors/couchbase3/src/main/scala/org/apache/pekko/stream/connectors/couchbase3/scaladsl/CouchbaseSource.scala:110:32: value analyticsQuery is not a member of com.couchbase.client.java.AsyncCluster
[error]       .completionStage(cluster.analyticsQuery(statement, options))
[error]     

• scalafmt issues
• missing Apache header on Example.scala

[laglangyue]

@pjfanning could you open the ci action in free time，I have tested it locally today. I would not add more api for dsl. maybe a doc pr plan was described in issues

[laglangyue]

@pjfanning PTAL, just a FTP flaky test failed. I have found a new job, so I currently do not have time to fix this issue of FTP.
I create a issue about FTP to record it, maybe in two weeks, I will do some deep digging for ftp
#627

[laglangyue]

Sorry, my response was a bit late. I changed my job and was very busy. The new job is not related to Pekko, so I can only participate in Pekko during my vacation at the moment.
I will process the review comments as soon as possible

[pjfanning]

Sorry, my response was a bit late. I changed my job and was very busy. The new job is not related to Pekko, so I can only participate in Pekko during my vacation at the moment. I will process the review comments as soon as possible

No Problem at all. Take your time. Thanks for your diligent work.

[laglangyue]

resolve conflict for build.sbt and rebase

[pjfanning]

lgtm

[pjfanning]

I've merged this but left #623 open because we'll need at least some doc changes to reflect the new cloudbase3 connector.