allow both [roles/]<role> queries

[manderson-it]

I love this project ❤️ I use it on a daily basis 😄
A small change for the following use cases, which I often run into.

tl;dr allow list-permissions-of-role to accept parameter as compute.networkUser or roles/compute.networkUser (the latter case allows for a copy and paste, see below).

# both work with this change
./list-permissions-of-role.sh roles/compute.networkUser
./list-permissions-of-role.sh compute.networkUser

Use case:
We see a permission error and need another IAM permission, e.g., compute.addresses.list.

We find suitable roles (around 54) with ./list-roles-with-permission.sh compute.addresses.list | sort -u.

Often, the next question is which of these roles is appropriate by looking into the set of permissions of a role; however, I cannot copy and paste the output from list-roles-with-permissions.sh to list-permissions-of-role.sh.