Don't fail when cleanup fails

[joshka]

Feature suggestion

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A detailed description of the proposed feature

Consider continuing rather than failing when brew cleanup fails. Report the errors at the end of the task rather than blocking completion.

The motivation for the feature

When running brew upgrade on a machine I hadn't touched in about a month, I was stopped 3 times due to an inability to remove an old openssl version:

Removing: /usr/local/Cellar/openssl/1.0.2q... (21 files, 8.4MB)
Error: Could not remove openssl keg! Do so manually:
  sudo rm -rf /usr/local/Cellar/openssl/1.0.2q

==> `brew cleanup` has not been run in 30 days, running now...
Removing: /usr/local/Cellar/openssl@1.1/1.1.1g... (8,073 files, 22MB)
Error: Could not remove openssl@1.1 keg! Do so manually:
  sudo rm -rf /usr/local/Cellar/openssl@1.1/1.1.1g

==> `brew cleanup` has not been run in 30 days, running now...
Removing: /usr/local/Cellar/openssl@1.1/1.1.1h... (8,081 files, 22.2MB)
Error: Could not remove openssl@1.1 keg! Do so manually:
  sudo rm -rf /usr/local/Cellar/openssl@1.1/1.1.1h

At this point, I ran brew cleanup manually rather than via upgrade, and got 3 more stop and try again errors. It would have been much easier to fix if I had the 3 rm commands to run in one step.

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

Any user that hits multiple cleanups would require less manually running several commands to proceed.

What alternatives to the feature have been considered

Automatically allow for cleanups like this by just removing the files (something like brew cleanup --force to perform the sudo rm)