Fix upload-sym to support uploading multiple files

[willkg]

Instead of uploading a single sym file at a time, I decided to fix upload-sym.py to support uploading multiple files in one upload pass. Then I used it to upload the jna symbols files just now.

It now supports:

bin/upload-sym.py --auth-token=xyz file1.sym file2.sym file3.sym ...

One nice thing you can do is use find or fd to upload a bunch of sym files in a directory regardless of where in the directory they are:

bin/upload-sym.py --auth-token=xyz $(find tmp/ "*.sym")

bin/upload-sym.py --auth-token=xyz $(fd ".*\.sym" tmp/)

[willkg]

Thank you!