Fix perf problems found in investigation of issue #107728

[davidwrighton]

• CheckRunClassInitThrowing didn't check to see if the class had been initialized before taking a lock
• EnsureTlsIndexAllocated didn't check if the Tls index had been allocated before setting the flag via an expensive Interlocked call to indicate that it had been allocated
• And finally JIT_GetNonGCThreadStaticBaseOptimized and JIT_GetGCThreadStaticBaseOptimized were missing the fast paths which avoided even calling those apis at all.

Perf with a small benchmark which does multithreaded work and is forced into the paths which hit this issue...

Runtime	Time
.NET 8	00.9414682 s
.NET 9 before this fix	22.8079382 s
.NET 9 with this fix	00.2004539 s

Fixes #107728

[davidwrighton]

Benchmark app for reference

using System.Diagnostics;
using System.Runtime.CompilerServices;

namespace DebugThreadStaticPerf
{
    internal class Program
    {
        [ThreadStatic]
        public static int X;
        public volatile static int ReadyThreads;
        public static int ReadyThreadCount = 6;
        public static int IterationCount = 100000;
        public static bool PreJit = WaitAndExecuteOnReadyThreads(1, 1);

        public volatile static int DoneThreads;

        [MethodImpl(MethodImplOptions.NoOptimization)]
        public static ref int GetThreadStatic()
        {
            return ref X;
        }

        [MethodImpl(MethodImplOptions.NoOptimization)]
        public static void ThreadProc()
        {
            WaitAndExecuteOnReadyThreads(ReadyThreadCount, IterationCount);
        }

        [MethodImpl(MethodImplOptions.NoOptimization)]
        public static bool WaitAndExecuteOnReadyThreads(int readyThreadCount, int iterationCount)
        {
            Interlocked.Increment(ref ReadyThreads);
            while (ReadyThreads != readyThreadCount)
            {

            }

            for (int i = 0; i < iterationCount; i++)
            {
                GetThreadStatic() = GetThreadStatic() + 1;
            }

            Interlocked.Increment(ref DoneThreads);

            return true;
        }

        [MethodImpl(MethodImplOptions.NoOptimization)]
        public static void TestFunction()
        {
            DoneThreads = 0;
            ReadyThreads = 0;

            List<Thread> threads = new List<Thread>();
            for (int i = 0; i < ReadyThreadCount; i++)
            {
                threads.Add(new Thread(ThreadProc));
                threads[i].Start();
            }

            while (DoneThreads != ReadyThreadCount)
            { }
        }

        [MethodImpl(MethodImplOptions.NoOptimization)]
        static Stopwatch RunTests(int iterationCount)
        {
            Stopwatch sw = new Stopwatch();
            sw.Start();
            for (int i = 0; i < iterationCount; i++)
                TestFunction();
            sw.Stop();
            return sw;
        }

        static void Main(string[] args)
        {
            RunTests(1);

            Console.WriteLine(RunTests(100).ToString());
            Console.WriteLine(RunTests(100).ToString());
            Console.WriteLine(RunTests(100).ToString());
            Console.WriteLine(RunTests(100).ToString());
            Console.WriteLine(RunTests(100).ToString());
        }
    }
}

[davidwrighton]

/backport to release/9.0

[github-actions]

Started backporting to release/9.0: https://github.com/dotnet/runtime/actions/runs/10857243727