Add ability for automatic URL path pattern discovery

When [the `use_path_as_transaction_name` config option](https://www.elastic.co/guide/en/apm/agent/java/current/config-http.html#config-use-path-as-transaction-name) is used, this can lead to transaction name explosion if path parameters are used. For this purpose, we also have [the `url_groups` config option](https://www.elastic.co/guide/en/apm/agent/java/current/config-http.html#config-url-groups), but it requires (possibly complex) user configuration.
By applying the algorithm presented [in this POC](https://github.com/eyalkoren/warehouse/tree/master/url-pattern-recognition/src/eyal/koren/url/recognition), the agent can auto-discover URL path patterns and use them as transaction names.

The additional advantage of implementing this now is that we will have the option of testing this algorithm, which we may want to employ in the future to facilitate head-based sampling.

Iniziate esaminando la documentazione esistente sulla configurazione di use_path_as_transaction_name e url_groups, quindi studiate la POC collegata sul riconoscimento dei pattern URL. Definite come i pattern rilevati debbano diventare nomi di transazione, aggiungete la copertura per l'algoritmo e la relativa integrazione e verificate che i percorsi parametrizzati non causino più un'esplosione dei nomi di transazione.

Scritto dal modello di indicizzazione a partire dal testo della issue.