Bitbucket cloud comments too long

[eh-am]

I believe this is similar to #280, but in our case, it's bitbucket cloud.

I am not completely sure it's the same error, but based on my experience, it usually happens when creating grafana dashboards (which output is huge).

2020/11/03 17:11:03+0000 [EROR] command_runner.go:537 $MY_ORG/$MY_REPO#32: Unable to comment: making request "POST https://api.bitbucket.org/2.0/repositories/$MY_ORG/$MY_REPO/pullrequests/32/comments" unexpected status code: 400, body: <h1>Bad Request (400)</h1> 

Based on the other issue, it seem breaking the comment down into multiple ones would a nice solution.

However, the biggest problem for us immediately is that there are no error messages being sent to bitbucket, requiring us to inspect atlantis logs to figure out what happened. So we would be fine with a "partial" solution.

I am running atlantis 0.14.0

Let me know if you need help with a PR (even though I haven't looked at the code yet).

[Almenon]

We have a similar issue. It's not large enough to generate 400 errors, but it's large enough to make the PR annoying to scroll through. One way to address this is to just avoid posting comments entirely. Just have a check that has a link to the build log on the Atlantis website, like how a CI/CD system like CircleCI does it.

Relevant: #936