formula_creator: add deny network for go and rust

[cho-m]

Create Go and Rust-based formulae with deny_network_access!. These account for majority of newly added formulae.

These require a separate fetch step.

For Rust, it matches our existing documentation. Testing functionality in Homebrew/homebrew-core#300798

For Go, it uses go mod download to fetch into cache that we defined. Testing functionality in Homebrew/homebrew-core#301819

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For remaining:

• Still looking into Cabal and Zig which I think support separate fetch phase.
• Python is complicated. May need to figure out how to handle PyPI build dependencies better.
• Not sure yet on Crystal, Node and Ruby.

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• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

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[Copilot]

Pull request overview

Adds offline Go and Rust formula templates using Homebrew’s separate dependency-fetch phase.

Changes:

• Generates fetch methods for Go and Rust dependencies.
• Denies build-time network access and enables Cargo offline installation.
• Adds template-generation coverage.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/formula_creator.rb	Generates offline Go and Rust build templates.
Library/Homebrew/test/formula_creator_spec.rb	Verifies generated fetch and network settings.

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[MikeMcQuaid]

Thanks @cho-m!