[lldb-dap] Improve `stackTrace` and `exceptionInfo` DAP request handlers (#105905)

Refactoring `stackTrace` to perform frame look ups in a more on-demand
fashion to improve overall performance.

[lldb-dap] Improve `stackTrace` and `exceptionInfo` DAP request handlers (#105905)

Refactoring `stackTrace` to perform frame look ups in a more on-demand
fashion to improve overall performance.

Additionally adding additional information to the `exceptionInfo`
request to report exception stacks there instead of merging the
exception stack into the stack trace. The `exceptionInfo` request is
only called if a stop event occurs with `reason='exception'`, which
should mitigate the performance of `SBThread::GetCurrentException`
calls.

Adding unit tests for exception handling and stack trace supporting.

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