Debugger: Register Widget bug fix. Block updates when changing types

Accomplished using `run-clang-tidy` with `performance-move-const-arg,performance-unnecessary-value-param,modernize-pass-by-value`.

Changed arguments to const references, removed them where inappropriate (e.g. sink parameters). Same with std::move.

Manually reviewed each change to make sure that it makes sense, and do something more appropriate if possible.

- Row height is no longer hardcoded to `24`; instead, the height is
  determined by the font height of the currently selected debug font.
- Header height has been reduced (a factor of the font height) as it
  only serves as a column resizer.
- A `OnDebugFontChanged()` slot has been connected to properly update
  the widget on debug font changes.

| Before | After |
| --- | --- |
| <img alt="Registers widget (before)" title="Registers widget (before)" src="https://github.com/user-attachments/assets/8a6644f9-1081-4ac8-9fff-c79ddb73e103" /> | <img alt="Registers widget (after)" title="Registers widget (after)" src="https://github.com/user-attachments/assets/67f799d0-8afd-4081-bb40-3d7a76ddc705" /> |

This will make the upcoming commits just a little bit neater to
implement.

When the interpreter calls MSRUpdated, we should update the membase
variable. Not because the interpreter itself needs it, but because the
JIT needs it if it's falling back to the interpreter for an instruction
that sets the MSR.

Additionally, the JIT's FallBackToInterpreter needs to read back the new
membase value afterwards.

This fixes games crashing on JitArm64 if mtmsr is set to fall back to
interpreter. I was unable to reproduce the issue on Jit64, presumably
due to a fortunate series of coincidences (instructions that set MSR are
always followed by an exception exit, and
PowerPCManager::CheckExternalExceptions was always calling
JitInterface::UpdateMembase, and Jit64::WriteExceptionExit was always
calling Jit64::EmitUpdateMembase.)