[llvm] [Dexter] Add missing calls to SBDebugger::{Initialize,Terminate} (PR #185535)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

Thanks for this! Would it be reasonable to move the `Initialize` and `Terminate` calls into `_custom_init` and `_custom_exit`? For context, the `LLDB` class will be initialized every time Dexter is run, even if LLDB isn't the debugger being used, so that Dexter can display info (whether or not it is present/valid and the version) if requested; any time we actually run the debugger, we use `with debugger`, which will call `_custom_init`.

Though with that said, if the call to `Initialize` is needed even to call `SBDebugger_GetVersionString`, then it may be necessarily to initialize in `__init__` (in which case LGTM).

https://github.com/llvm/llvm-project/pull/185535