Implements verifier and code gen for swift (#6373)

Updates test cases on linux

Adhere to new protocol naming

Adds fuzzing

Adds documentation

Adds support for string unions

Updated fuzzer generated code

tests/FlatBuffers.Test.Swift/Sources/SwiftFlatBuffers/fuzzer.fbs

@@ -0,0 +1,32 @@
+enum Color:ubyte (bit_flags) {
+  Red = 0, // color Red = (1u << 0)
+  /// \brief color Green
+  /// Green is bit_flag with value (1u << 1)
+  Green,
+  /// \brief color Blue (1u << 3)
+  Blue = 3,
+}
+
+struct Test { a:short; b:byte; }
+
+struct Vec3 (force_align: 8) {
+  x:float;
+  y:float;
+  z:float;
+  test1:double;
+  test2:Color;
+  test3:Test;
+}
+
+/// an example documentation comment: "monster object"
+table Monster {
+  pos:Vec3 (id: 0);
+  hp:short = 100 (id: 2);
+  mana:short = 150 (id: 1);
+  name:string (id: 3, key);
+  color:Color = Blue (id: 6);
+  inventory:[ubyte] (id: 5);
+  testarrayoftables:[Monster] (id: 4);
+}
+
+root_type Monster;