Title: Export unique symbol list with llvm-nm new option "--export-symbols"

Title: Export unique symbol list with llvm-nm new option "--export-symbols"

Summary:

the patch implement of following functionality.
1. export the symbols from archive or object files.
2. sort the export symbols. (based on same symbol name and visibility)
3. delete the duplicate export symbols (based on same symbol name and visibility)
4. print out the  unique and sorted export symbols (print the symbol name and visibility).

there are two new options are add in the patch
1. --export-symbols (enable the functionality of export unique symbol)
2. --no-rsrc (exclude the symbol name begin with "__rsrc" from be exporting from xcoff object file)

Export symbol list for xcoff object file has the same functionality as
The patch has the same functionality as
https://www.ibm.com/docs/en/xl-c-aix/13.1.0?topic=library-exporting-symbols-createexportlist-utility

Reviewers: James Henderson,Fangrui Song
Differential Revision: https://reviews.llvm.org/D112735