Improve output of brew upgrade not upgrading pinned tasks #24136

Verification

• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.
• I did not use AI/LLM to create this issue, or I disclosed the tool and model used; I will answer maintainer questions myself without AI/LLM.

Provide a detailed description of the proposed feature

The output of brew upgrade should show available versions.

brew upgrade
==> Auto-updating Homebrew...
==> 2 Pinned casks
docker-desktop 4.88.1,237512
vmlx 1.6.45
Warning: Not upgrading 2 pinned packages:
docker-desktop 4.88.1,237512, vmlx 1.6.45
==> 2 Pinned casks
docker-desktop 4.88.1,237512
vmlx 1.6.45

What is the motivation for the feature?

The output of brew upgrade is not very helpful as it shows the pinned version of packages three times, but does not show the available version even once. I've pinned the version of these packages since they have too many huge upgrades available too often.

How will the feature be relevant to at least 90% of Homebrew users?

Ability to decide whether I should manually upgrade the pinned package.

What alternatives to the feature have been considered?

I don't think there are any alternatives.