toml-spanner: No, we have "Serde" at home. Incremental compilation benchmarks and more

With the toml-spanner 1.0 release, it is now a fully featured TOML crate will all the features you'd expect but one, Serde.

When I posted earlier in development, one of the feature requests I got was full Serde integration, at the time I explained I had other plans. Now that those plans have come to completion this post evaluates the cost and benefits of going our own way, looking at the incremental complication benefits, workaround we can avoid
and bugs fixed.

Edit: Blog Post: https://i64.dev/toml-spanner-no-we-have-serde-at-home/
(Apparently on new Reddit, it looks like an image post.)