Bug 1797840: Replace stray tab characters with spaces in IDL files throughout...

Bug 1797840: Replace stray tab characters with spaces in IDL files throughout the tree. r=mccr8,necko-reviewers,credential-management-reviewers,smaug,sgalich,valentin

DONTBUILD because this is just whitespace cleanup.

I found the files to fix up here using this command:
    grep -r '   ' * 2>/dev/null | grep -v "other-licenses" | grep "idl:"

I replaced the tab characters with however many spaces seemed consistent with
the indentation in the surrounding code (and did some minor space-indentation
cleanup in contextual lines to preserve alignment, in a few cases).

Differential Revision: https://phabricator.services.mozilla.com/D160577