Android: Wait for surface in Run

Rename GetDefaultBackendName to GetDefaultBackendConfigName to
distinguish it from the display name.

There are two hard problems in computer science...

Fulfilling a certain six-year-old todo.

Accessible from DolphinQt and Android.

This reverts the revert commit bc67fc97c39628c76a4dbca411b0e8a9bfaf726a,
except for the changes in BaseConfigLoader.cpp, which caused the bug
that made us revert 72cf2bdb87f09deff22e1085de3290126aa4ad05. PR 12917
contains an improved change to BaseConfigLoader.cpp, which can be merged
(or rejected) independently.

A few changes have also been made based on review comments.

When we boot the core, it needs to have a valid surface to draw graphics
to. Our Kotlin code does wait for a valid surface to exist before it
calls NativeLibrary.Run, but there's a chance for the surface to be
deleted before Run locks s_surface_lock. If that happens, the core boots
without a valid surface, which presumably would cause a crash. (I
haven't been able to reproduce the problem myself.)

In a race condition, the core could shut down between the `JitInterface::GetCore` nullptr check and the `JitInterface::JitBlockLogDump` call which constructs a `CPUThreadGuard`. In this scenario, nothing horrible happens—`JitBlockLogDump` also checks for a nullptr—but it would be a failure to display the correct feedback to the user.