TiFlash's max thread is not set to correct value

[CalvinNeo]

Bug Report

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[CalvinNeo]

It is reported that TiFlash has a performance regression because it creates a thread pool of the size std::thread::hardware_concurrency(), rather than what we get from proxy.

The reason is that the value of SettingMaxThreads depends on Proxy, for

struct SettingMaxThreads
{
...
    void setAuto()
    {
        value = getAutoValue();
        is_auto = true;
    }

    static UInt64 getAutoValue()
    {
        auto res = getNumberOfLogicalCPUCores();
        return res;
    }

So if the setNumberOfLogicalCPUCores is not called before getAutoValue is called, then it will be set to std::thread::hardware_concurrency() which could cause the problem.

namespace CPUCores
{
UInt16 number_of_logical_cpu_cores = std::thread::hardware_concurrency();
UInt16 number_of_physical_cpu_cores = std::thread::hardware_concurrency() / 2;
} // namespace CPUCores


UInt16 getNumberOfLogicalCPUCores()
{
    return CPUCores::number_of_logical_cpu_cores;
}

void setNumberOfLogicalCPUCores(UInt16 number_of_logical_cpu_cores_)
{
    CPUCores::number_of_logical_cpu_cores = number_of_logical_cpu_cores_;
}

The problem is directly caused by https://github.com/pingcap/tiflash/pull/9753/files#diff-b5cd81d9e6eb39780d8ba3b54869c02eaa40da60d3ec2a55b4d1c229eedd3eed, which makes proxy depend on Settings.h.