Some of the paths ignored by `test-core.yaml` need to be checked by
`make check`. The `checks.yaml` workflow run on these paths and can also
be used as a reusable workflow.
Many of our scripts have a non-portable interpreter line for bash and
use bash-specific variables like `BASH_SOURCE`. Update the interpreter
line to be portable between various Linuxes and macOS without
complaint from posix shell users.
Also format terraform scripts with hclfmt, equivalent to terraform fmt.
I opted not to use terraform fmt, because I didn't want to introduce dev dependency on the terraform CLI.
Also, I've optimized the find command to ignore spurious directories (e.g. .git, node_modules) that seem to be populated with too many files! make hclfmt takes 0.3s on my mac down from 7 seconds!
