Lua Generator using IR. (#6940)

* initial hack to get new Lua generator into flatc

* Starting to output enum defs for Lua

* Continue to work on table generation for Lua

* Finished basic getter access for Lua

* Added ability to get object by index

* Finished struct builder

* aliased reflection to r

* finish table builder generation

* register requiring files

* better generated header info

* Tying up loose ends

* Updated reflection to handle struct padding

* Addd type sizes to reflection

* Fixed some vector indirect issues

* Lua tests passed

* Misc cleanup

* ci fixes 1

* ci fixes 2

* renaming

* up size of type sizes

* manually ran clang-format-11 -i src/idl_parser.cpp

* fixed some windows casting

* remove stupid auto import

* more static_casting

* remove std

* update other build environments

* remove scoped enums

* replaced std::to_string with NumToString

* more win fixes

* more win fixes

* replaced old lua with new

* removed auto import

* review responses

* more style fixes

* refactor bfbs_gen_len to use code +=

* added consts

* fix lambda capture for windows

* remove unused return type

reflection/reflection.fbs

@@ -38,6 +38,10 @@ table Type {
                      // If base_type == Union, UnionType, or integral derived
                      // from an enum, index into "enums" below.
     fixed_length:uint16 = 0;  // Only if base_type == Array.
+    /// The size (octets) of the `base_type` field.
+    base_size:uint = 4; // 4 Is a common size due to offsets being that size.
+    /// The size (octets) of the `element` field, if present.
+    element_size:uint = 0;
 }
 
 table KeyValue {
@@ -77,6 +81,8 @@ table Field {
     attributes:[KeyValue];
     documentation:[string];
     optional:bool = false;
+    /// Number of padding octets to always add after this field. Structs only.
+    padding:uint16 = 0; 
 }
 
 table Object {  // Used for both tables and structs.