Small DX improvements that goes with#60105 and#60083.

This PR adds two new methods,first() andlast(), added to JsonPath builder. This voluntary reminds methods from the DomCrawler component. The goal is not to add every possible method, but I thinkfirst() andlast() are common enough to be added.

I also propose to renameanyIndex() toall().

$path =newJsonPath();// Get the first user of the collection$path =$path->key('users')->first();

$path =newJsonPath();// Get the last user of the collection$path =$path->key('users')->last();

$path =newJsonPath();// Get all users of the collection$path =$path->key('users')->all();