Avoids pointless copies

We can just take the value parameter by value which allows both moving
into it, and copies at the same time, depending on the calling code.

These operators don't modify internal class state, so they can be made
const member functions. While we're at it, drop the unnecessary inline
keywords. Member functions that are defined in the class declaration are
already inline by default.

This provides the equivalent behavior, but without as much boilerplate.
While we're at it, explicitly default the move constructor, since we
have a move-assignment operator defined.

This makes it consistent with most of the other private utility
functions.

This doesn't actually modify the internal class state, so it can be a
const member function. While we're at it, amend the function to take
its arguments by const reference.

QString initializes to an empty string by default, so this does nothing
meaningful. While we're at it, use a constructor initializer list for
initializing the gamelist member variable.

There's no need to perform a separate resize.

A few member functions didn't actually modify class state, so these can
be amended as necessary.

This also potentially avoids warnings, considering the copy assignment
operator is supposed to have a return value.

We were trying to delete things in the current directory instead of the actual filesystem directory. This may fix some savedata issues in some games.

The GPU ignores that register when clearing, but OpenGL obeys the glDepthMask parameter, so we set the depth mask to GL_TRUE when clearing the depth buffer. It will be restored to the correct value automatically on the next draw call.

* More improvements to GDBStub
- Debugging of threads should work correctly with source and assembly level stepping and modifying registers and memory, meaning threads and callstacks are fully clickable in VS.
- List of modules is available to the client, with assumption that .nro and .nso are backed up by an .elf with symbols, while deconstructed ROMs keep N names.
- Initial support for floating point registers.

* Tidy up as requested in PR feedback

* Tidy up as requested in PR feedback

- When VertexA shader stage is enabled, we combine with VertexB program to make a single Vertex Shader stage.