Add allowlistedCertificates field to TrustConfig

[modular-magician]

This CL adds allowlistedCertificates field to TrustConfig resource.
Fixes #18170 and #18385

Tests that I run:
make testacc TEST=./google/services/certificatemanager TESTARGS='-run=TestAccCertificateManagerTrustConfig_certificateManagerTrustConfigAllowlistedCertificatesExample'

make testacc TEST=./google/services/certificatemanager TESTARGS='-run=TestAccCertificateManagerTrustConfig_update'

Manual tests that I performed:

• Create a resource with one allowlisted
• Add one more cert to the resource
• Remove one cert from the resoruce

Release Note Template for Downstream PRs (will be copied)

certificatemanager: added `allowlisted_certificates` to `google_certificate_manager_trust_config`

Derived from GoogleCloudPlatform/magic-modules#10906

[github-actions]

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