Converts lingering panic alert calls over to the fmt-capable ones.

Migrates over to the fmt-capable logger.

Some users who get this error don't seem to gain much understanding
of how to resolve the problem from reading the error message.

These are only ever used with ShaderCode instances and nothing else.
Given that, we can convert these helper functions to expect that type of
object as an argument and remove the need for templates, improving
compiler throughput a marginal amount, as the template instantiation
process doesn't need to be performed.

We can also move the definitions of these functions into the cpp file,
which allows us to remove a few inclusions from the ShaderGenCommon
header. This uncovered a few instances of indirect inclusions being
relied upon in other source files.

One other benefit is this allows changes to be made to the definitions
of the functions without needing to recompile all translation units that
make use of these functions, making change testing a little quicker.

Moving the definitions into the cpp file also allows us to completely
hide DefineOutputMember() from external view, given it's only ever used
inside of GenerateVSOutputMembers().

glReadPixels() with depth formats is not supported.

Should fix broken EFB access on GLES.

Consolidate the NVIDIA Tegra and non-Tegra checks into one branch.

Now that we've extracted all of the stateless functions that can be
hidden, it's time to make the index generator a regular class with
active data members.

This can just be a member that sits within the vertex manager base
class. By deglobalizing the state of the index generator we also get rid
of the wonky dual-initializing that was going on within the OpenGL
backend.

Since the renderer is always initialized before the vertex manager, we
now only call Init() once throughout the execution lifecycle.

Previously the logging was a in a little bit of a disarray. Some things
were in namespaces, and other things were not.

Given this code will feature a bit of restructuring during the
transition over to fmt, this is a good time to unify it under a single
namespace and also remove functions and types from the global namespace.

Now, all functions and types are under the Common::Log namespace. The
only outliers being, of course, the preprocessor macros.