Fix Row-Vector Distribution test failures

[andrjohns]

Summary

@WardBrian pointed out that the distribution tests have been failing since #2784 was merged. This was because I'd assumed that only std::vector<int> types would be passed as the vectorised form for int, but the distribution tests also pass Eigen::RowVector int types.

This PR updates the handling of the bernoulli CDF functions to make sure that dimensionality is not assumed.

Tests

N/A

Side Effects

N/A

Release notes

Fix distribution test failures with row-vector integer inputs to bernoulli CDF functions

Checklist

• Math issue #(issue number)

• Copyright holder: Andrew Johnson

  The copyright holder is typically you or your assignee, such as a university or company. By submitting this pull request, the copyright holder is agreeing to the license the submitted work under the following licenses:
  - Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
  - Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

• the basic tests are passing

  • unit tests pass (to run, use: ./runTests.py test/unit)
  • header checks pass, (make test-headers)
  • dependencies checks pass, (make test-math-dependencies)
  • docs build, (make doxygen)
  • code passes the built in C++ standards checks (make cpplint)

• the code is written in idiomatic C++ and changes are documented in the doxygen

• the new changes are tested

[WardBrian]

I just started https://jenkins.flatironinstitute.org/blue/organizations/jenkins/Stan%2FMath/detail/PR-2954/2/pipeline and manually enabled the row vector tests that get run on develop, so if that passes this should be good!

Thanks for being so quick on this!