Use patchable rdtsc sequence to avoid slowdowns under rr

We (Julia) ship both support for using tracy to trace julia applications,
as well as using `rr` (https://github.com/rr-debugger/rr) for record-replay debugging.
After our most recent rebuild of tracy, users have been reporting signfificant performance
slowdowns when `rr` recording a session that happens to also load the tracy library
(even if tracing is not enabled). Upon further examination, the recompile happened
to trigger a protective heuristic that disabled rr's patching of tracy's use of
`rdtsc` because an earlier part of the same function happened to look like a
conditional branch into the patch region. See https://github.com/rr-debugger/rr/pull/3580
for details. To avoid this issue occurring again in future rebuilds of tracy,
adjust tracy's `rdtsc` sequence to be `nopl; rdtsc`, which (as of of the
linked PR) is a sequence that is guaranteed to bypass this heuristic
and not incur the additional overhead when run under rr.

This functionality is kept behind a compile-time flag `TRACY_PATCHABLE_NOPSLEDS`
in order to avoid polluting the instruction cache unnecessarily.

CMakeLists.txt

@@ -78,6 +78,7 @@ set_option(TRACY_NO_VERIFY "Disable zone validation for C API" OFF)
 set_option(TRACY_NO_VSYNC_CAPTURE "Disable capture of hardware Vsync events" OFF)
 set_option(TRACY_NO_FRAME_IMAGE  "Disable the frame image support and its thread" OFF)
 set_option(TRACY_NO_SYSTEM_TRACING  "Disable systrace sampling" OFF)
+set_option(TRACY_PATCHABLE_NOPSLEDS  "Enable nopsleds for efficient patching by system-level tools (e.g. rr)" OFF)
 set_option(TRACY_DELAYED_INIT "Enable delayed initialization of the library (init on first call)" OFF)
 set_option(TRACY_MANUAL_LIFETIME "Enable the manual lifetime management of the profile" OFF)
 set_option(TRACY_FIBERS "Enable fibers support" OFF)