Remove trailing whitespace and convert tabs to space

[jdumas]

A lot of files have a mix of tabs and space, so converting tabs to 8-spaces in bulk. Similarly I trimmed any trailing whitespace.

You can ignore whitespace to make sure I've only edited whitespaces in this PR.

Ideally we'd have clang-format enabled in github action to make sure files are consistently formatted, but I guess that's a topic for another time :)