[C++] Add Command-Line Flag to Suppress MIN and MAX Enums (#7705)

Add the --no-minmax-values flag to prevent flatc from generating C++
enums with MIN and MAX enumerated values that otherwise would be set
to the inclusive lower and upper bound respectively of the enum.

This command-line flag is needed to avoid collisions when an enum that
is being ported to FlatBuffers already has a MIN or MAX enumerated
value.

It is also needed to work around a long-standing problem with
magic_enum that causes magic_enum to not see enumerated values that
are not unique.  For example, if FlatBuffers sets MIN = FOO and MAX =
BAR, MIN and FOO share the same underlying value so they are not
unique.  The same is true of MAX and BAR.  This prevents magic_enum
from converting FOO and BAR to and from strings as well as causing
magic_enum to return a count of enumerated values that is two fewer
than it should be.

Co-authored-by: Paul Serice <paul@serice.net>

docs/source/Compiler.md

@@ -90,7 +90,10 @@ Additional options:
 
 -   `--scoped-enums` : Use C++11 style scoped and strongly typed enums in
     generated C++. This also implies `--no-prefix`.
-
+    
+-   `--no-emit-min-max-enum-values` : Disable generation of MIN and MAX
+    enumerated values for scoped enums and prefixed enums.
+    
 -   `--gen-includes` : (deprecated), this is the default behavior.
                        If the original behavior is required (no include
 	                   statements) use `--no-includes.`