Constructor of `SonarLintEngine` should not produce any side-effects

[algomaster99]

Reference: #696 (comment)

We recreate the analysis engine whenever we fetch the singleton instance of SonarLintEngine. That's bad for two reasons.

1. There should not be any side-effect when we fetch the singleton instance.
2. Recreation is necessary for tests so we should instead refactor our tests to invoke recreateAnalysisEngine before each test case.