More install/upgrade checks needed? (fileinfo)

[sbulen]

Description

You get a pretty hard fail if you do not have fileinfo enabled in php.ini. I thought we had a check for that, but apparently not.

We should ensure the upgrader checks are consistent, too. Double-check that mbstring is checked in installer & upgrader as well.

Forum discussion:
https://www.simplemachines.org/community/index.php?topic=579810.0

Steps to reproduce

1. Install current version. Update avatar in a profile, specifying using an avatar by URL.

Environment (complete as necessary)

• Version/Git revision: Current
• Database Type: mysql
• Database Version: 8.0.20
• PHP Version: 8.0.13

Additional information/references

If fileinfo is disabled, you white screen with:

[sbulen]

I really don't think this is a 2.1.0 requirement. Could we remove or change the milestone?

Note this is already listed in the install requirements.