Emit a proper diagnostic for unknown -Zself-profile-events values

[bjorn3]

Currently it only emits a warn!() log, which is not shown by default.

rust/compiler/rustc_data_structures/src/profiling.rs

Lines 596 to 604 in 55d4364

	warn!(
	"Unknown self-profiler events specified: {}. Available options are: {}.",
	unknown_events.join(", "),
	EVENT_FILTERS_BY_NAME
	.iter()
	.map(|&(name, _)| name.to_string())
	.collect::<Vec<_>>()
	.join(", ")
	);