tdx: conditionally check debug registers for hardware interrupts when GDB feature is enabled

[niranjanthyagaraja]

This change introduces a feature gate for the gdb feature in the HW_INTERRUPTand EXCEPTION handling code. The change ensures that thebreakpoint_debug_exceptionis only set when thegdb` feature is enabled. This avoids unnecessary kernel interactions when debugging is not enabled.

[niranjanthyagaraja]

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[smalis-msft]

Looks good to me, but will need to be cleaned up to pass the fmt CI.