JSX: plain and preserve mode evaluate children and props in different orders #9104

Found by a bug hunt over the 16 commits from eb087382 to cd641cbc.

let el = <div title={note("t")} key={note("k")}> {React.string(note("c"))} </div>

• Plain mode emits jsx("div", {children: note("c"), title: note("t")}, note("k")), which evaluates c, t, k.
• Preserve mode emits <div key={note("k")} title={note("t")}>{note("c")}</div>, which after the usual JSX transform (TypeScript react-jsx) evaluates t, c, k.

Plain mode builds the props record in the record type's declaration order (translcore.ml#L1692-L1694). JsxDOM.domProps declares children second (JsxDOM.res#L23), so in plain mode children are evaluated before almost every attribute. The same holds for a component whose props type declares children before other fields. tests/build_tests/jsx_preserve_semantics checks that the two modes agree, but never logs children against an attribute. The JS is the same at b123b7c3.

Related: #8757 (the dict-spread ordering case that suite covers).

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