Rename getStructFieldOffset/Type() parameter

By convention, parameter names of camel case methods should also
be camel case, i.e. the name should be $fieldName rather than
$field_name.

However, following GH-7236, which changed $arg_index to just $index,
this also changes $field_name to just $name. The fact that it is
a field name is obvious from context.

ext/ffi/ffi.stub.php

@@ -87,8 +87,8 @@ public function getArrayLength(): int {}
     public function getPointerType(): CType {}
 
     public function getStructFieldNames(): array {}
-    public function getStructFieldOffset(string $field_name): int {}
-    public function getStructFieldType(string $field_name): CType {}
+    public function getStructFieldOffset(string $name): int {}
+    public function getStructFieldType(string $name): CType {}
 
     public function getFuncABI(): int {}
     public function getFuncReturnType(): CType {}

ext/ffi/ffi_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 2675462a253edd2a0ea6106b9640f0d1a5a09489 */
+ * Stub hash: 82f586480d2b29e6aa359f7080cdc7ea092a1ecc */
 
 ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_class_FFI_cdef, 0, 0, FFI, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, code, IS_STRING, 0, "\"\"")
@@ -104,11 +104,11 @@ ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_class_FFI_CType_getStructFieldNa
 ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_class_FFI_CType_getStructFieldOffset, 0, 1, IS_LONG, 0)
-	ZEND_ARG_TYPE_INFO(0, field_name, IS_STRING, 0)
+	ZEND_ARG_TYPE_INFO(0, name, IS_STRING, 0)
 ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_class_FFI_CType_getStructFieldType, 0, 1, FFI\\CType, 0)
-	ZEND_ARG_TYPE_INFO(0, field_name, IS_STRING, 0)
+	ZEND_ARG_TYPE_INFO(0, name, IS_STRING, 0)
 ZEND_END_ARG_INFO()
 
 #define arginfo_class_FFI_CType_getFuncABI arginfo_class_FFI_CType_getKind