Remove legacy VM service version checks and fallbacks

[helin24]

This PR is work in preparation for removing usages of the DAS for debugging in the Flutter plugin. There are some checks for VM service version that are no longer relevant since the version is over two years old.

To test this manually, check these debugging scenarios:

• Stopping at a breakpoint in Flutter app, Flutter test
• Navigating in stack frame shows the right places in code
• Pausing on exceptions

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[gemini-code-assist]

Code Review

This pull request simplifies VmServiceWrapper by removing deprecated fallback logic for setting isolate pause modes and mapping breakpoints, which relied on older VM service versions. Specifically, it removes supportsSetIsolatePauseMode(), addBreakpointWithMapper(), and the VmServiceVersion class, standardizing on modern VM service APIs. The review feedback suggests refactoring the addBreakpoint method to adhere to the style guide's 30-line limit and optimizing the loop in setExceptionPauseMode by reusing a single stateless SetIsolatePauseModeConsumer instance instead of instantiating it repeatedly.

[pq]

Sweet!

[auto-submit]

autosubmit label was removed for flutter/flutter-intellij/9144, because - The status or check suite checker (VERIFY_BOT) has failed. Please fix the issues identified (or deflake) before re-applying this label.