Unbreak tests/ui/lint/use_suggestion_json.rs.

PR rust-lang#82639 changed UI tests so `-Z unstable-options` aren't passed to UI
tests by default. This completely broke `use_suggestion_json.rs`, which
uses the unstable `--error-format=pretty-json` option. The expected
output went from 400 lines of pretty JSON error messages to a single
JSON error saying "`--error-format=pretty-json` is unstable"!

This commit adds `-Z unstable-options` back and reinstates the old
expected output, with some minor changes to account for shifted spans
and slightly JSON output changes since then.

Author: nnethercote

tests/ui/lint/use_suggestion_json.rs

@@ -1,6 +1,6 @@
 // ignore-windows
 // ignore-sgx std::os::fortanix_sgx::usercalls::alloc::Iter changes compiler suggestions
-// compile-flags: --error-format pretty-json --json=diagnostic-rendered-ansi
+// compile-flags: --error-format pretty-json --json=diagnostic-rendered-ansi -Z unstable-options
 
 // The output for humans should just highlight the whole span without showing
 // the suggested replacement, but we also want to test that suggested