and_then support in simdjson_result for monadic operations about simdjson HOT 2 OPEN

We already support chaining in our main API (on demand). Screenshot from our documentation:

We do not support chaining arbitrary lambda expressions, although it could be added with ease if there is a use case for it.

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I think that chaining refers wrt to nesting of the fields but another way could be to parse fields at the same level of nesting.

I maybe wrong but there's no simple exception free way to check for error without checking each field.

{"a":1, "b":2}

If I want to parse a and then b, I have to check for error twice in each step. With and_then, it's easier as you can focus on error free path and handle errors at last.

One way is to have a variable for each key and then use get() in succession but feels terse than just using and_then

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