ci: try running diff-shades runs concurrently (#4767)

* ci: try running diff-shades runs concurrently

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

* fix unable to merge origin main

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

* add merge-multiple: true

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

* merge analysis back into one
because it needs to be one in case projects are different based off of cache

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

* split it up again, but pull from the cache for baseline projects list
idk why i combined it back tbh lol

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

* add the comment back

Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>

* Update diff_shades_gha_helper.py

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Signed-off-by: cobalt <61329810+cobaltt7@users.noreply.github.com>