[NFC] Gardening. (#27581)

Remove unused known protocols (`TensorProtocol`, `TensorFlowDataTypeCompatible`)
and helper functions.

Author: dan-zheng

include/swift/AST/KnownProtocols.def

@@ -84,8 +84,6 @@ PROTOCOL(ElementaryFunctions)
 PROTOCOL(KeyPathIterable)
 PROTOCOL(TensorArrayProtocol)
 PROTOCOL(TensorGroup)
-PROTOCOL_(TensorFlowDataTypeCompatible)
-PROTOCOL(TensorProtocol)
 PROTOCOL(VectorProtocol)
 PROTOCOL(Differentiable)
 PROTOCOL(EuclideanDifferentiable)

lib/AST/ASTContext.cpp

@@ -1066,8 +1066,6 @@ ProtocolDecl *ASTContext::getProtocol(KnownProtocolKind kind) const {
   // SWIFT_ENABLE_TENSORFLOW
   case KnownProtocolKind::TensorArrayProtocol:
   case KnownProtocolKind::TensorGroup:
-  case KnownProtocolKind::TensorFlowDataTypeCompatible:
-  case KnownProtocolKind::TensorProtocol:
     M = getLoadedModule(Id_TensorFlow);
     break;
   case KnownProtocolKind::Expression:

lib/IRGen/GenMeta.cpp

@@ -4224,8 +4224,6 @@ SpecialProtocol irgen::getSpecialProtocolID(ProtocolDecl *P) {
   case KnownProtocolKind::KeyPathIterable:
   case KnownProtocolKind::TensorArrayProtocol:
   case KnownProtocolKind::TensorGroup:
-  case KnownProtocolKind::TensorFlowDataTypeCompatible:
-  case KnownProtocolKind::TensorProtocol:
   case KnownProtocolKind::VectorProtocol:
   case KnownProtocolKind::Differentiable:
   case KnownProtocolKind::EuclideanDifferentiable:

lib/SILOptimizer/Mandatory/Differentiation.cpp

@@ -220,11 +220,11 @@ static CanType joinElementTypesFromValues(SILValueRange &&range,
 static FuncDecl *findOperatorDeclInProtocol(DeclName operatorName,
                                             ProtocolDecl *protocol) {
   assert(operatorName.isOperator());
-  // Find the operator requirement in the `VectorProtocol` protocol
-  // declaration and cache it.
+  // Find the operator requirement in the given protocol declaration.
   auto opLookup = protocol->lookupDirect(operatorName);
-  // Find the `+` with type siguature `(Self, Self) -> Self`.
   for (auto *decl : opLookup) {
+    if (!decl->isProtocolRequirement())
+      continue;
     auto *fd = dyn_cast<FuncDecl>(decl);
     if (!fd || !fd->isStatic() || !fd->isOperator())
       continue;
@@ -875,9 +875,6 @@ class ADContext {
   /// The AdditiveArithmetic protocol in the standard library.
   ProtocolDecl *additiveArithmeticProtocol =
       astCtx.getProtocol(KnownProtocolKind::AdditiveArithmetic);
-  /// The VectorProtocol protocol in the standard library.
-  ProtocolDecl *vectorProtocolProtocol =
-      astCtx.getProtocol(KnownProtocolKind::VectorProtocol);
 
   /// `AdditiveArithmetic.+` declaration.
   mutable FuncDecl *cachedPlusFn = nullptr;
@@ -933,10 +930,6 @@ class ADContext {
     return additiveArithmeticProtocol;
   }
 
-  ProtocolDecl *getVectorProtocolProtocol() const {
-    return vectorProtocolProtocol;
-  }
-
   FuncDecl *getPlusDecl() const {
     if (!cachedPlusFn) {
       cachedPlusFn = findOperatorDeclInProtocol(