OProfile is not used at all these days, most major distributions do not ship it anymore (Debian, Fedora, and Alpine to name the few I've checked) and following a discussion on Discord, nobody is apparently using it, most devs not even being aware of it. This removes an optional dependency from Dolphin.

Makes the namespace consistent with other common utilities.

Prefer fmt to printf-style formatting.

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

Begins the transition to using fmt for string formatting where
applicable. Given fmt supports formatting std::string instances out of
the box, we can remove now-unnecessary calls to .c_str() and .data().

Note that this change does not touch the actual logging subsystem aside
from converting the final StringFromFormat call in the process over to
fmt::format. Given our logging system is heavily used throughout the
entire codebase, and converting that over will be quite a large change
by itself, this will be tackled near the end of the conversion process.

With tons of symbols, this results in noticeable stuttering, so
skip lookups if the perf dir option isn't set anyway.

Reduces the number of files that need to be recompiled
when making changes to FileUtil.h.