Add test examples for regional targetProxies to resources google_network_services_tls_route

[rostislavbobo]

Add the targetProxies field to TLSRoute resource.

Fixes hashicorp/terraform-provider-google#26490

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 2 files changed, 104 insertions(+))
google-beta provider: Diff ( 4 files changed, 248 insertions(+))

[github-actions]

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