BREAKING CHANGE!: next/image only allow quality 75 by default (#83175)
## Background
We have default allowlists for the `url` (localPatterns/remotePatterns
config) and `w` (imageSizes/deviceSizes config) but we don't have a
default allowlist for `q` (currently opt-in with via qualities config).
## What's changing?
BREAKING CHANGE: This PR is a breaking change that sets the default
allowlist to `qualities: [75]`, meaning that anything other than 75 is
invalid. Since most images don't set the quality prop and therefore
default to 75, most apps will be unaffected.
However, we can be even more gracious when users upgrade because we can
coerce the value automatically to 75 (or rather any value in `qualities`
allowlist). In dev, this will print a warning explaining why the prop
was not observed. This also works if you had `qualities` configured but
removed 75, since the closet matching value in the array will be used
instead.