Update gutters on config-reload and :set gutters

[A-Walrus]

Resolves #3445

[archseer]

Hmm, since each view has it's own set of gutters the idea was you could use :set per view to change gutters. Do we have access to the old config value? Then we could only update buffers that have the old default set of gutters.

[A-Walrus]

the idea was you could use :set per view to change gutters.

This feels kind of counter intuitive to me. If the :set command is defined as setting a config option, it should be equivalent to reloading with a changed config. Having it act on a specific view for only this specific option seems like inconsistent behavior. Maybe there should be a separate command for per-view changes?

[pascalkuthe]

closing this one as stale, this will be covered by #8853. Thank you for contributing!