Move functions from func.d to funcsem.d. (#16286)

These require `import dscope` that we want to remove from func.d in pursuit of https://github.com/orgs/dlang/projects/41.

Other functions that still need to be moved include `overloadApply()`, `isUnique()` and `equals()`, the latter needing a visitor akin #15782.

compiler/src/dmd/dclass.d

@@ -26,6 +26,7 @@ import dmd.dsymbol;
 import dmd.dsymbolsem;
 import dmd.errors;
 import dmd.func;
+import dmd.funcsem;
 import dmd.id;
 import dmd.identifier;
 import dmd.location;

compiler/src/dmd/declaration.d

@@ -27,6 +27,7 @@ import dmd.dtemplate;
 import dmd.errors;
 import dmd.expression;
 import dmd.func;
+import dmd.funcsem;
 import dmd.globals;
 import dmd.gluelayer;
 import dmd.id;

compiler/src/dmd/dmangle.d

@@ -147,6 +147,7 @@ import dmd.dtemplate;
 import dmd.errors;
 import dmd.expression;
 import dmd.func;
+import dmd.funcsem;
 import dmd.globals;
 import dmd.id;
 import dmd.identifier;

compiler/src/dmd/dstruct.d

@@ -28,6 +28,7 @@ import dmd.dtemplate;
 import dmd.errors;
 import dmd.expression;
 import dmd.func;
+import dmd.funcsem;
 import dmd.globals;
 import dmd.id;
 import dmd.identifier;

compiler/src/dmd/escape.d

@@ -25,6 +25,7 @@ import dmd.dsymbol;
 import dmd.errors;
 import dmd.expression;
 import dmd.func;
+import dmd.funcsem;
 import dmd.globals : FeatureState;
 import dmd.id;
 import dmd.identifier;

compiler/src/dmd/frontend.h

@@ -3786,7 +3786,6 @@ class FuncDeclaration : public Declaration
     bool isCodeseg() const final override;
     bool isOverloadable() const final override;
     bool isAbstract() final override;
-    bool canInferAttributes(Scope* sc);
     void initInferAttributes();
     PURE isPure();
     bool isSafe();
@@ -3806,7 +3805,6 @@ class FuncDeclaration : public Declaration
     bool checkClosure();
     bool hasNestedFrameRefs();
     static bool needsFensure(FuncDeclaration* fd);
-    void buildEnsureRequire();
     ParameterList getParameterList();
     static FuncDeclaration* genCfunc(Array<Parameter* >* fparams, Type* treturn, const char* name, StorageClass stc = 0);
     static FuncDeclaration* genCfunc(Array<Parameter* >* fparams, Type* treturn, Identifier* id, StorageClass stc = 0);