Remove `execaCommand()`

[ehmicky]

See #1016 and #1054

execaCommand() and execaCommandSync() have been deprecated in favor of parseCommandString(). Their documentation has been removed. However, their implementation and types have been kept for backward compatibility.

In the next major release, those methods should be completely removed.

As an internal cleanup task, we will also want to remove the file and commandArguments returned by the internal function mapArguments(), since this is only used by execaCommand().

execa/lib/methods/create.js

Lines 53 to 58 in 62d02af

	const {
	file = initialFile,
	commandArguments = initialArguments,
	options = mergedOptions,
	isSync = false,
	} = mapArguments({file: initialFile, commandArguments: initialArguments, options: mergedOptions});