IAM ServiceAccount Roles: truncate name at 64 characters

[justinsb]

The maximum IAM role name length is 64 characters, which we hit much
more often now that we are constructing complex names. Use our normal
strategy of adding a hash when we truncate.

This is not a breaking change, because these names were not valid
previously.

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[justinsb]

This is intended to fix the scenario test: https://k8s-testgrid.appspot.com/google-aws#kops-grid-scenario-public-jwks

[hakman]

Seems related to #10382.
/cc @rifelpet

[rifelpet]

/lgtm
for reference, this will truncate the offending iam role name from

dns-controller.kube-system.sa.e2e-kops-scenario-public-jwks.test-cncf-aws.k8s.io

to

dns-controller.kube-system.sa.e2e-kops-scenario-public-jw-ucdio5

which i think provides enough of the cluster name to still be useful to users viewing an account's list of IAM roles.