Rollup merge of #97389 - m-ou-se:memory-ordering-diagnostics, r=estebank
Improve memory ordering diagnostics
Before:
![image](https://user-images.githubusercontent.com/783247/170234545-891cac30-eaa2-4186-847b-35cd51e00f2b.png)
After:
![image](https://user-images.githubusercontent.com/783247/170239684-645f186f-5a02-4eb9-8651-2e5fe9591352.png)
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Before this change, the compiler suggests the failure ordering is too strong and suggests choosing a weaker ordering. After this change, it instead suggests the success ordering is not strong enough, and suggests chosing a stronger one. This is more likely to be correct.
Also, before this change, the compiler suggested downgrading an invalid AcqRel failure ordering to Relaxed, without mentioning Acquire as an option.