Update code so that the `warn_return_any` check passes.

1. If a value is of type ArrayAttribute then append '[]' to the name
   of the value for query parameters (`params`).

This is step 3 in a series of steps of our goal to add full
support for the GitLab API data types[1]:
  * array
  * hash
  * array of hashes

Step one was: commit 5127b1594c00c7364e9af15e42d2e2f2d909449b
Step two was: commit a57334f1930752c70ea15847a39324fa94042460

Fixes: #1698

[1] https://docs.gitlab.com/ee/api/#encoding-api-parameters-of-array-and-hash-types

This can be used to tell if a `RESTObject` was created using
`lazy=True`.

Add a message to the `AttributeError` if attribute access fails for an
instance created with `lazy=True`.

Commit b6447211754e126f64e12fc735ad74fe557b7fb4 inadvertently
introduced a possible breaking change as it added a new argument
`iterator` and added it in between existing (potentially positional) arguments.

This moves the `iterator` argument to the end of the argument list and
requires it to be a keyword-only argument.

* feat(downloads): allow streaming downloads access to response iterator

Allow access to the underlying response iterator when downloading in
streaming mode by specifying `iterator=True`.

Update type annotations to support this change.

* docs(api-docs): add iterator example to artifact download

Document the usage of the `iterator=True` option when downloading
artifacts

* test(packages): add tests for streaming downloads

Enable the pylint check "no-else-return" and fix the errors detected.