Upgrade C# linter to support linting multiple files at a time

Summary:
This upgrades `cslint` to support linting multiple files at a time.  As this required a backwards-incompatible to `cslint`, I've added a SUPPORTED_VERSION constant which can be used to detect these kinds of breaking changes in the future (and prompt users to upgrade the `cslint` they have in their repository).

The reason for this upgrade is mainly around running `arc lint --everything`, where there are significant performance benefits gained when bulk linting lots of files per command execution.

Test Plan: Upgraded `cslint` in the Tychaia repository and ran `arc lint --everything --trace`.  Saw a substantially less number of executions happening for linting and all of the results came through as expected.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran, waynea

Differential Revision: https://secure.phabricator.com/D7599