Allow setting a title for the created check run

[garyttierney]

This change allows a workflow to contain multiple clippy-check
invocations that execute in parallel, by giving each run a unique name.

Previously, any clippy invocations running in parallel would race
against each other, and annotaions would only reported for the first to
hit createCheck(...).

[garyttierney]

The alternative to this approach is aggregating each clippy-check invocation into a single check run.

There are some problems with this:

• There needs to be a single invocation responsible for setting the conclusion, this would require tracking pending clippy runs or the user configuring the last invocation in a serial workflow.
• You would be unable to run multiply clippy invocations in parallel, since they'd still be racing against createCheck(...).
• Generating summaries for multiple check runs would require fetching the published data from the initial runs and appending on top, or modifying them in some way.

[svartalf]

I am pretty much okay with this change, but I think it is worth to point that this "input" is a temporary solution for one specific problem and it will be deprecated as soon as Github will implement the Action Annotations.