[Nim] Bfbs Nim Generator (#7534)

* Bfbs Nim Generator

* Remove commented out tests

* add missing line to idl.h

* Commit python reflection changes

* Commit python reflection changes and move tests

* Remove default string addition

* Move tests to python file

* Fix element size check when element is table

* remove whitespace changes

* add element_type docs and commit further to namer and remove kkeep

* Bfbs Nim Generator

* Remove commented out tests

* add missing line to idl.h

* Commit python reflection changes

* Commit python reflection changes and move tests

* Remove default string addition

* Move tests to python file

* Fix element size check when element is table

* remove whitespace changes

* add element_type docs and commit further to namer and remove kkeep

* remove unused variables

* added tests to ci

* added tests to ci

* fixes

* Added reflection type Field, Variable to namer

* Moved reflection namer impl to bfbsnamer

* Remove whitespace at end of line

* Added nim to generated code

* Revert whitespace removal

Co-authored-by: Derek Bailey <derekbailey@google.com>

nim/flatbuffers/src/struct.nim

@@ -0,0 +1,24 @@
+import table
+
+
+type FlatObj* {.inheritable.} = object
+   tab*: Vtable
+
+func Table*(this: var FlatObj): Vtable = this.tab
+
+func Init*(this: var FlatObj; buf: seq[byte]; i: uoffset) =
+   this.tab.Bytes = buf
+   this.tab.Pos = i
+
+# Cant define it in table.nim since it needs FlatObj and Init
+func GetUnion*[T: FlatObj](this: var Vtable; off: uoffset): T =
+   result.Init(this.Bytes, this.Indirect(off))
+
+func GetRootAs*(result: var FlatObj; buf: seq[byte]; offset: uoffset) =
+   var
+      vtable = Vtable(Bytes: buf[offset..^1], Pos: offset)
+      n = Get[uoffset](vtable, offset)
+   result.Init(buf, n+offset)
+
+func GetRootAs*(result: var FlatObj; buf: string; offset: uoffset) =
+   result.GetRootAs(cast[seq[byte]](buf), offset)