Add diffing support to results

The internal GitHub developer tooling includes custom views of published mismatch data that calculates diffs of the values. It could be helpful to include that diffing support directly via Diff::LCS and generating diffs of pretty-inspected (and cleaned) values.

Ref: #84

该 issue 未指定任何文件或测试；首先跟踪已发布的 mismatch 数据和自定义结果视图是如何表示的，然后阅读 #84 中的上下文，并评估提议的 Diff::LCS 集成。完成的标准是：结果提供经过 pretty-inspect 和清理的值的 diff，并在相关的结果覆盖范围中验证其行为。

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