Update http and git sources only once

[bugadani]

This PR is supposed to fix this nonsense by checking if a remote registry has already been updated, where the check was missing before.

[Copilot]

Pull request overview

This PR aims to prevent redundant updates of remote package sources within a single Cargo session by tracking which sources have already been updated in GlobalContext::updated_sources().

Changes:

• Add is_updated/mark_updated helpers to HTTP sparse registry handling and use them to short-circuit repeated “update” work.
• Add is_updated/mark_updated helpers to git dependency handling and use them to avoid re-updating when resolving a deferred git reference multiple times in one session.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/cargo/sources/registry/http_remote.rs	Adds per-session updated-source tracking and attempts to skip repeated HTTP registry update setup.
src/cargo/sources/git/source.rs	Adds per-session updated-source tracking and avoids repeated git updates when resolving deferred refs.

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