feat: split codex-common into smaller utils crates

[bolinfest]

We are removing feature-gated shared crates from the codex-rs workspace. codex-common grouped several unrelated utilities behind [features], which made dependency boundaries harder to reason about and worked against the ongoing effort to eliminate feature flags from workspace crates.

Splitting these utilities into dedicated crates under utils/ aligns this area with existing workspace structure and keeps each dependency explicit at the crate boundary.

What changed

• Removed codex-rs/common (codex-common) from workspace members and workspace dependencies.
• Added six new utility crates under codex-rs/utils/:
  • codex-utils-cli
  • codex-utils-elapsed
  • codex-utils-sandbox-summary
  • codex-utils-approval-presets
  • codex-utils-oss
  • codex-utils-fuzzy-match
• Migrated the corresponding modules out of codex-common into these crates (with tests), and added matching BUILD.bazel targets.
• Updated direct consumers to use the new crates instead of codex-common:
  • codex-rs/cli
  • codex-rs/tui
  • codex-rs/exec
  • codex-rs/app-server
  • codex-rs/mcp-server
  • codex-rs/chatgpt
  • codex-rs/cloud-tasks
• Updated workspace lockfile entries to reflect the new dependency graph and removal of codex-common.