[mlir] Convert raw data in dense element attributes for big-endian machines.

This patch fixes a bug [[ https://bugs.llvm.org/show_bug.cgi?id=46091 | 46091 ]]

Raw data for the `dense-element attribute` is written in little endian (LE) format.
This commit converts the format to big endian (BE) in ʻAttribute Parser` on the
 BE machine. Also, when outputting on a BE machine, the BE format is converted
 to LE in "AsmPrinter".

Differential Revision: https://reviews.llvm.org/D80695