Adjust how `slang` and `slangc` uses a `profile` to manage the stage of an entry-point (#4670)

* Fixes #4656

Changes:
1. Setting a profile via slangc no-longer sets an entry-point target-stage, this is to allow slangc to follow how the SLANG-API works (else `main` is assumed to be the default entry-point)
2. If the stage specified by a profile is not equal to the stage specified by a entry-point, we throw a capability error.
3. Resolving the stage of an entry point was changed to function (mostly) equally for when 0 entry-points are specified versus to when there are 1 or more.
4. changed capabilitySet Iterator so it is invalid if backing data is nullptr (although this should never happen, it would stop crashes in the worst case).

* remove the breaking change since it likely is going to be a lot more than just a simple change due to the implicit `main` and stage through `profile` code.

* print out profile name with errors

* use target's profile for printing

* change logic to print warning in a different method (account for more cases)

* set unknown stages

1 files changed, 36 insertions, 0 deletions

diff --git a/tests/language-feature/capability/conflicting-profile-stage-for-entry-point.slang b/tests/language-feature/capability/conflicting-profile-stage-for-entry-point.slang
new file mode 100644
index 000000000..9cc06347f
--- /dev/null
+++ b/tests/language-feature/capability/conflicting-profile-stage-for-entry-point.slang
@@ -0,0 +1,36 @@
+//TEST:SIMPLE(filecheck=CHECK_ERROR): -target spirv -entry psmain -profile vs_6_0
+//TEST:SIMPLE(filecheck=CHECK_ERROR): -target spirv -entry vsmain -profile ps_6_0
+
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -entry vsmain -profile vs_6_0
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -entry psmain -profile vs_6_0 -ignore-capabilities
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -entry vsmain -profile ps_6_0 -ignore-capabilities
+
+// CHECK_ERROR: warning 36112
+// CHECK-NOT: warning 36112
+
+struct CameraProperties {
+    float4x4 MVP;
+};
+
+[[vk::push_constant]]
+ConstantBuffer<CameraProperties> Cam;
+
+struct VSOutput {
+    float4 PositionCS : SV_POSITION;
+    float3 Color      : COLOR;
+};
+
+[shader("vertex")]
+VSOutput vsmain(float3 PositionOS : POSITION, float3 Color : COLOR0)
+{
+    VSOutput output = (VSOutput)0;
+    output.PositionCS = mul(Cam.MVP, float4(PositionOS, 1));
+    output.Color = Color;
+    return output;
+}
+
+[shader("pixel")]
+float4 psmain(VSOutput input) : SV_TARGET
+{
+    return float4(input.Color, 1);   
+}
\ No newline at end of file