[Scheduling] Logging via the containing op can be too verbose

Nobody has claimed this yet.

@7FM noted:
> I find the logging sometimes a bit too verbose, especially when the `containingOp` is very large. A hacky workaround that I sometimes use OoT is something like `mlir::emitError(OpBuilder{mlirContext}.getUnknownLoc()) << "Some context info:" << "your error message"`.
> Some examples that might benefit from this approach:
> - https://github.com/llvm/circt/blob/main/lib/Scheduling/Problems.cpp#L124C12-L127
> - https://github.com/llvm/circt/blob/main/lib/Scheduling/Problems.cpp#L183-L187
> - https://github.com/llvm/circt/blob/main/lib/Scheduling/Problems.cpp#L282-L285
>
> Most of the time, the error messages are not directly related to the containing operation itself but rather to the way the scheduling problem was constructed.

_Originally posted by @7FM in https://github.com/llvm/circt/pull/7320#pullrequestreview-2198730405_

Start in lib/Scheduling/Problems.cpp at the diagnostic sites around lines 124-127, 183-187, and 282-285. Read how scheduling errors are currently emitted and check nearby tests or diagnostic conventions before changing them. Done means these errors retain useful context without printing an unnecessarily large containing operation.

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