ensure balrog has all the updates needed to support ESR91

esr78 prior art in Bug 1647634

"There doesn't seem to be a rule for the esr-localtest-next channel that points to the 78.0esr build
so instead Balrog is offering 69.10.0esr
probably missing an entry at https://hg.mozilla.org/releases/mozilla-esr78/file/tip/taskcluster/ci/release-balrog-submit-toplevel/kind.yml#l49"

we might need to s/78/91/ and s/69/78/

at the very least we should ensure via using balrog and grepping through code that all references to ESR, and 78 are handled properly

I've created firefox-esr91-localtest and firefox-esr91-cdntest rules on balrog on the test channels, and an esr91 rule on the esr channel. The in-tree bits to update these rules are taken care of in bug 1717540.