Improve DevTools protocol version handling

# How does DevTools work and what is the "protocol version"? The React DevTools extension consists of multiple pieces: * The **frontend** portion is the extension you see (the Components tree, the Profiler, etc.). * The **backend** portion is invisible. It runs in the same context as React itself. The frontend displays the current React tree, but it has no way to observe the tree directly because it runs in different memory space. It relies on the backend to describe the tree by sending "messages" through an API like [`postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage). The most optimized way for the backend to share the state of the React tree is to send a small packet of ["op codes"](https://github.com/facebook/react/blob/main/packages/react-devtools/OVERVIEW.md#serializing-the-tree) whenever the tree changes (e.g. whenever React DOM modifies the page). These "op codes" are just an array of numbers which correspond to _operations_ like "add something to the tree" or "remove something from the tree". For example, the operation to add a component to the tree might look like this: ```js [ // ... 1, // number 1 signifies an "add" operation 2, // component id 1, // type: class component 1, // parent id 0, // owner id 1, // id of component display name (corresponds to the string table) 0, // id of key string in the string table (zero indicates no key) // ... ] ``` The format described above is highly optimized but also inflexible. (For example, if the backend needs to add an additional piece of information to the above operation, the frontend needs to also know to advance its index within the operations array by one additional place.) DevTools version 4.13 introduced the concept of a [_protocol version number_](https://github.com/facebook/react/pull/21331) to allow the frontend to ask the backend which version of the protcol it used. In hindsight, **this number should have included in the operations array i…