Allow callers to provide their own executor in the TimeoutedLessCompiler

[a701440]

In the spirit of allowing the caller to control how threads are created and managed in the application allow to provide the Executor implementation in the Configuration and use that instead of the hard-coded executor.

[SomMeri]

It could also be just another parameter in constructor. In any case, I will add that for the next release (or would accept pull request too).