Add Google Workspace provider

[danielblignaut]

Summary

• Add Google Workspace provider with Gmail send/check and Calendar create/check tools
• Add real Google Workspace e2e coverage using OAuth client test secrets to mint access tokens before CLI invocation
• Update docs/catalog output for the provider

Checks

• make test-provider-tool PROVIDER=google-workspace TOOL=gmail-send
• make test-provider-tool PROVIDER=google-workspace TOOL=gmail-check
• make test-provider-tool PROVIDER=google-workspace TOOL=calendar-create
• make test-provider-tool PROVIDER=google-workspace TOOL=calendar-check
• make test-provider PROVIDER=google-workspace
• make test-unit
• make test-e2e
• make generate-docs
• make generate-catalog
• make build

Harness experiment: exp_4b83a548-18c

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