Adding Eventarc GoogleChannelConfig Resource support for TPG

[modular-magician]

I have made changes to the magic-modules repo to support a new resource the Eventarc team has created, called GoogleChannelConfig. It is a regional singleton resource that enables customers to proctect their data with encryption for all first party triggers.

Fixes: hashicorp/terraform-provider-google#12520

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• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
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• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
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Release Note Template for Downstream PRs (will be copied)

google_eventarc_google_channel_config

Derived from GoogleCloudPlatform/magic-modules#6534