fix(typescript): show message when check-types has no components to check

[davidfirst]

When bit check-types runs without finding any components (e.g., all are exported), it now shows a helpful message similar to other commands like bit test:

no components found to check.
use "--unmodified" flag to check all components or specify the ids to check.
otherwise, only new and modified components will be checked

Also added the component count to the success message for better feedback.

[Copilot]

Pull request overview

This PR enhances the bit check-types command to provide better user feedback when no components are found to check. It aligns the behavior with similar commands like bit test and bit build by showing an informative message that explains why no components were checked and how to check all components. Additionally, it adds component count information to the success message.

Key Changes:

• Added handling for empty component lists with helpful guidance message
• Enhanced success message to include the count of checked components
• Modified runDiagnosticOnTsServer to return both tsserver instance and component count

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[davidfirst]

Addressing Copilot review comments:

1. Type safety for null return: Fixed by using undefined instead of null, which matches the return type of getTsserverClient() (TsserverClient | undefined).

2. Pluralization: Keeping the component(s) format for consistency with other commands in the codebase.