SRE-527: Add Terraform and TFLint Renovate rules

[TimDiekmann]

Summary

Add shared Renovate package rules for Terraform-based repos:

• Terraform providers: branch prefix deps/tf/, no dashboard approval, assigned to @TimDiekmann
• required_version: disabled (Terraform CLI version controlled via mise)
• TFLint plugins: branch prefix deps/tflint/, no dashboard approval, assigned to @TimDiekmann

Part of setting up Renovate in hashintel/internal-infra.

Test plan

• Merge this, then verify internal-infra Renovate picks up the rules from shared config

[augmentcode]

🤖 Augment PR Summary

Summary: Adds shared Renovate package rules to better manage IaC updates for Terraform and TFLint.

Changes:

• Adds a Terraform provider update rule (branch prefix deps/tf/, no dashboard approval, assigned to @TimDiekmann)
• Disables Renovate bumps for Terraform required_version (Terraform CLI version is controlled via mise)
• Adds a TFLint plugin update rule (branch prefix deps/tflint/, no dashboard approval, assigned to @TimDiekmann)

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[augmentcode]

Review completed. 1 suggestions posted.

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[augmentcode]

matchDepTypes: ["provider"] only targets the deprecated Terraform provider blocks; most repos on Terraform >=0.13 pin providers via required_providers (depType required_provider), so this rule may not apply to the intended dependencies.

Severity: medium

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