Support for ANY_USER_ACCOUNT in module vpc-sc egress rule.

[xjantoth]

This PR enables to support keyword ANY_USER_ACCOUNT when crafting VPC SC egress rule.
This keyword (identity_type) is currently not enabled by validation block in modules/vpc-sc/variable.tf.

Despite the fact that this option is specifically not enabled by fast vpc-sc module, it is indeed fully supported by underlying terraform resource google_access_context_manager_service_perimeters.

Desired state:

I applicable, I acknowledge that I have:

[ x] Read the contributing guide
[ x] Ran terraform fmt on all modified files
[ x] Regenerated the relevant README.md files using tools/tfdoc.py
[ x] Made sure all relevant tests pass

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[juliocc]

Nice catch. Thanks for the fix @xjantoth!

Can you sign the CLA so we can go ahead and merge it?

[juliocc]

Can you sign the CLA so we can go ahead and merge it?

Ignore, you already did :)