Support an Upper-case variant of [NumThreads] and [Shader] (#4780)

Closes #4746.

This commit adds a support for "NumThreads" and "Shader" attribute keyword, which is in CamelCasing starting with an upper case letter.

The attribute keywords in HLSL are case-insensitive. As an example, one of D3D documents says,

"The attribute name "Shader" is case insensitive."
https://microsoft.github.io/DirectX-Specs/d3d/WorkGraphs.html

Slang, however, doesn't support the case-insensitivity. They should be all lower-case or CamelCasing starting with an upper case.

source/slang/core.meta.slang

@@ -2590,6 +2590,9 @@ attribute_syntax [call]                 : CallAttribute;
 __attributeTarget(FuncDecl)
 attribute_syntax [shader(stage)]    : EntryPointAttribute;
 
+__attributeTarget(FuncDecl)
+attribute_syntax [Shader(stage)]    : EntryPointAttribute;
+
 // Hull Shader
 __attributeTarget(FuncDecl)
 attribute_syntax [maxtessfactor(factor: float)]     : MaxTessFactorAttribute;
@@ -2625,6 +2628,9 @@ attribute_syntax [earlydepthstencil]    : EarlyDepthStencilAttribute;
 __attributeTarget(FuncDecl)
 attribute_syntax [numthreads(x: int, y: int = 1, z: int = 1)]   : NumThreadsAttribute;
 
+__attributeTarget(FuncDecl)
+attribute_syntax [NumThreads(x: int, y: int = 1, z: int = 1)]   : NumThreadsAttribute;
+
 __attributeTarget(FuncDecl)
 attribute_syntax [WaveSize(numLanes: int)]   : WaveSizeAttribute;
 

tests/compute/frem.slang

@@ -19,7 +19,8 @@ int test(int inVal)
 //TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
 RWStructuredBuffer<float> outputBuffer;
 
-[numthreads(4, 1, 1)]
+[Shader("compute")]
+[NumThreads(4, 1, 1)]
 void computeMain(int3 dispatchThreadID : SV_DispatchThreadID)
 {
 	int tid = dispatchThreadID.x;