Support specifying replacement formulae in deprecate! or disable! calls

[carlocab]

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.

Provide a detailed description of the proposed feature

A formula might do

deprecate! date: "3000-03-30", because: :unmaintained

or similarly with disable!. When this is set, brew info will show

Deprecated because it is not maintained upstream! It will be disabled on 3001-03-30.

We should add a new, optional, kwarg called replacement:, like so:

deprecate! date: "3000-03-30", because: :unmaintained, replacement: "better-software"

which will change the deprecation message to something like

Deprecated because it is not maintained upstream! It will be disabled on 3001-03-30.
Consider replacing it with:
    brew install better-software

What is the motivation for the feature?

Some formulae are deprecated and replaced by a formula of a different name. For example, exa and eza.

See also discussion at Homebrew/homebrew-core#183953.

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

It might not be, but it'll improve the experience of users of formulae that are deprecated/disabled.

What alternatives to the feature have been considered?

Leaving our handling of deprecate! and disable! unchanged.

[MikeMcQuaid]

Great idea.

[alebcay]

Implemented in #18733, shipped in https://github.com/Homebrew/brew/releases/tag/4.4.5, documented in #18810.