Update workflows

Update the GitHub actions workflows using a subset of the changes
from the master branch, commit 620a977f22. Cherry-picking each
relevant commit would have resulted in a large number of conflicts
so this change only applies a minimal set of useful updates.

• Added build-dependencies.txt and checkstyle-dependencies.txt
• Added reclaim_disk_space.sh script
• Minor changes to build steps
• Reduced ztest run time
• checkbashisms, mandoc, and cppcheck were not included to avoid additional backports
• Add exceptions for shellcheck

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>