Introduce parameter failOnMismatchedAllowedViolationsCount

### New feature, improvement proposal

Associated PR: https://github.com/apache/maven-checkstyle-plugin/pull/165

Introduce a parameter to fail the build when the number of violations is not equal to maxAllowedViolations

This prevents the following scenario:
- some changes reduce the checkstyle count but maxAllowedViolations is not updated
- some other changes introduces new violations but the build does not fail, as the count left some margin for error, when we would like to avoid introducing new failures

Review the associated pull request at https://github.com/apache/maven-checkstyle-plugin/pull/165 to understand the proposed parameter and its current status. The change is done when the Maven Checkstyle Plugin can fail when the violation count differs from maxAllowedViolations, preventing both unreported new violations and an outdated allowance.

Written by the indexing model from the issue text.