In John 14:16, according to the Catholic Church, who is the Spirit of Truth? "And I will ask the Father, and He will give you another Advocate to be with you forever – the Spirit of truth" (John 14:16–17, NIV)


From Jesus' words the Spirit of Truth is the Holy Spirit, but if we consider the succeeding verses below, it seems like it's describing the role of the Holy Spirit as a Teacher of Faith and someone who will testify in full about who Jesus is.


  But the Advocate, the Holy Spirit, whom the Father will send in My name, will teach you all things and will remind you of everything I have told you. 
  (John 14:26)
  
  When the Advocate comes, whom I will send to you from the Father — the Spirit of truth who goes out from the Father — He will testify about Me.
  (John 15:26)


My question is: according to Catholic teaching, is the Spirit of Truth a person in whom the Holy Spirit chose to dwell, to testify to and become the teacher and guide of the Apostles?
The Catholic Church holds that the "Spirit of Truth" here is simply the Holy Spirit:


  When he proclaims and promises the coming of the Holy Spirit, Jesus calls him the "Paraclete," literally, "he who is called to one's side," advocatus. "Paraclete" is commonly translated by "consoler," and Jesus is the first consoler. The Lord also called the Holy Spirit "the Spirit of truth." (Catechism, §692)


This section cites the verses you quote and a few others (John 14:16, 14:26, 15:26, 16:7, and 16:13) in support of its statements, so it's fair to say that this is how these passages are understood.  The Catholic Commentary on Sacred Scripture, though not as official as the Catechism, states in relation to John 16:13:


  The Holy Spirit is the Spirit of Truth (14:17; 15:26) because he leads the disciples to understand in faith the meaning of Jesus' revelation. (source)