Fixup switch warning; Use count_limit2; Benchmark ghostrider before flex

[Spudz76]

Fix spam during compilation:

/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp: In member function ‘virtual xmrig::CpuThreads xmrig::BasicCpuInfo::threads(const xmrig::Algorithm&, uint32_t) const’:
/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp:393:12: warning: enumeration value ‘INVALID’ not handled in switch [-Wswitch]
  393 |     switch (algorithm.id()) {
      |            ^
/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp:393:12: warning: enumeration value ‘CN_0’ not handled in switch [-Wswitch]
/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp:393:12: warning: enumeration value ‘CN_1’ not handled in switch [-Wswitch]
/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp:393:12: warning: enumeration value ‘CN_2’ not handled in switch [-Wswitch]
/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp:393:12: warning: enumeration value ‘CN_R’ not handled in switch [-Wswitch]
/usr/src/xmrig/src/backend/cpu/platform/BasicCpuInfo.cpp:393:12: warning: enumeration value ‘CN_FAST’ not handled in switch [-Wswitch]
...

Also use count_limit2 like everything else does, and do ghostrider before flex in benchmarking (in case the subalgo optimization test/selections matter).

[MoneroOcean]

Thank you!