CVE-2024-39697: panic on parsing crafted phonenumber inputs

The phonenumber parsing code may panic due to a reachable assert! guard on the phonenumber string.

In a typical deployment of rust-phonenumber, this may get triggered by feeding a maliciously crafted phonenumber, e.g. over the network, specifically strings of the form +dwPAA;phone-context=AA, where the “number” part potentially parses as a number larger than 2^56.

Since f69abee1/0.3.4/#52.

0.2.x series is not affected.