Improve updates of auto_updates casks

[MikeMcQuaid]

• Add HOMEBREW_NO_UPGRADE_AUTO_UPDATES_CASKS enviroment variable to disable this behaviour entirely
• Output this (and other relevant variables and flags) as environment hints with the usual option to disable their output
• Detect and provide workaround instructions for casks with broken metadata directories during the upgrade process rather than blowing it up

Improves changed behaviour from #21882
Closes #21961
Fixes #21951
Fixes #21958

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Hand coded.

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[Copilot]

Pull request overview

This PR adjusts Homebrew Cask upgrade behavior around auto_updates true casks by adding an opt-out environment variable, surfacing relevant environment “hints” during upgrades, and attempting to avoid hard failures when installed cask metadata can’t be loaded.

Changes:

• Add HOMEBREW_NO_UPGRADE_AUTO_UPDATES_CASKS EnvConfig entry and Sorbet RBI for disabling auto-updates bundle staleness upgrades.
• Update cask upgrade messaging to print environment/flag hints (with HOMEBREW_NO_ENV_HINTS suppression).
• Change upgrade flow to skip (with guidance) casks whose installed caskfile can’t be loaded, instead of aborting the entire upgrade.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 5 comments.

File	Description
Library/Homebrew/sorbet/rbi/dsl/homebrew/env_config.rbi	Adds Sorbet signatures for new env config accessors (but currently includes an extra accessor without runtime backing).
Library/Homebrew/env_config.rb	Registers HOMEBREW_NO_UPGRADE_AUTO_UPDATES_CASKS in EnvConfig.
Library/Homebrew/cask/upgrade.rb	Prints new env hints and changes handling of invalid/unloadable installed cask metadata during upgrade.
Library/Homebrew/cask/cask.rb	Uses the new env var to short-circuit auto_updates_bundle_outdated?.

Files not reviewed (1)

• Library/Homebrew/sorbet/rbi/dsl/homebrew/env_config.rbi: Language not supported

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[MikeMcQuaid]

@yudgnahk Please slow down. You've opened 2 PRs and posted 3 nearly identical comments. Will review a follow-up PR to add 2 non-integration tests, thanks, as long as you've reviewed your AI output first.

[yudgnahk]

Sorry @MikeMcQuaid, it's a mistake.