Support "replace" utility function

Similar to the "modify" function, but allowing the key to be changed too.

The two use cases I have in mind for this is:

• Renaming a key in-place while retaining the existing value
• Replacing an existing key/value with new key/value in the same place

Of course, the existing modify function could be overloaded to support this, but I suggest a new function because:

• It's not valid to supply the root for a replace
• The meaning of undefined value param changes

Example of how this would look if "replace" is implemented:

/**
 * Computes the edit operations needed to replace a key/value in the JSON document.
 * 
 * @param documentText The input text 
 * @param path The path of the value to change. The path represents either to a property or an array item.
 * If the path points to an non-existing property or item, an error will be thrown. 
 * @param key The new key name for the specified property or item.
 * @param value The new value for the specified property or item. If the value is undefined,
 * the existing value will be retained.
 * @param options Options
 * @returns The edit operations describing the changes to the original document, following the format described in {@linkcode EditResult}.
 * To apply the edit operations to the input, use {@linkcode applyEdits}.
 */
export function replace(text: string, path: JSONPath, key: string, value: any, options: ModificationOptions): EditResult;

Start by reviewing the existing "modify" function and its handling of paths, keys, and undefined values. Define the replace behavior for renaming a key, replacing a key/value, rejecting the root path, and retaining the value when it is undefined; done means the exported function produces the documented edit operations for those cases.