Make it easy to fine-tune the Sonar's Delphi default ruleset

### Prerequisites

- [X] This improvement has not already been suggested.
- [X] This improvement would be generally useful, not specific to my code or setup.
- [X] This improvement is not related to analysis quality (e.g. new rules, improvements to existing rules), which should be raised on the [SonarDelphi repository](https://github.com/integrated-application-development/sonar-delphi/issues).

### Engine area

Delphi IDE integration

### Improvement description

In the settings dialog "Standalone Mode tab" the option "Use SonarDelphi's default ruleset" is selected. When then the user selects "Use a custom ruleset" all rules are selected. It would be better, I think if only the rules of the default ruleset were selected, so that the user can fine-tune the ruleset, by adding/removing rules.

### Rationale

Typically the user wants to adjust the default ruleset, rather than specifying from scratch a new ruleset. The default ruleset is a better starting point for that, compared to starting with all rules selected.