When did Christians begin to understand that the articles in the temple were foreshadows of Jesus? For example the bread on the Showbread table is a foreshadow of Jesus as the "Bread of Life". Did the disciples teach this principal? Did this thinking come later as the books of the Bible were collated?
I cannot give you a break down of every single foreshadow interpretation and when it was first taught. What I can say is that this was already an important means of interpretation of the New Testament writers. There are many examples of this. Jesus said in John 3:14 that the snake lifted up by Moses in the desert (Numbers 21:4-9) was a foreshadow of his being lifted up on the cross. He also said that the entire Old Testament was, at least in some sense about him (John 5:39-40). Jesus saw the three days Jonah was inside the big fish as a prefigure of his three days in the heart of the earth (before this even happened to him!). Many other examples of Jesus seeing himself as the fulfillment of types and foreshadows can be mentioned.
Paul used Old Testament people and events as foreshadows of New Testament things many times. A good example is Galatians 4:21-21 where he specifically says that these things (Abraham, Isaac, Ishmael, Sarah and Hagar) "may be taken figuratively." In Romans 4 he noted that Abraham is a "type" of all those who would believe by faith. Many other examples can be listed.
Peter looks at several Old Testament events and people as foreshadows of New Testament teachings and of the ministry of Jesus. Examples include 1 Peter 3:20-22 where he calls the water in the flood a symbol of the water of baptism which now saves us, as it saved Noah and his family from destruction. He identifies Sodom and Gomorrah as a foreshadow of judgment (2 Peter 2:5-7) and the flood of Noah a foreshadow of final judgment (2 Peter 3:3-7).
The most prolific user of foreshadowing from the Old Testament to New Testament things is the writer of Hebrews. Hebrews is loaded with this sort of thing. He calls the wandering in the wilderness and their seeking of rest in Canaan a foreshadow of our future rest with God (Heb 3 and 4). He calls the items in the Tabernacle a copy and a shadow of things to come (Hebrews 9:1-9). Let me draw your attention in particular to Hebrews 9:11 where the writer says that the items in the tabernacle, "things that are already here," are a picture of the more perfect heavely tabernacle. Also, Hebrews 10:1 actually calls the things in the Law, shadows. There are dozens of examples of use of foreshadows from the Old Testament and their fulfilled meaning in Jesus in Hebrews.
We also know that the early church fathers continued with this method of interpretation. Sometimes they went too far, using allegorical interpretation which is not warranted by the original text. Origen and Clement of Alexandria can be accused of this method. Augustine often used prefigures and foreshadows to explain the relationship between the Old and New Testaments. I was at a presentation just last month at which a scholar of ancient writing techniques pointed out that the production of codices, which were book-like manuscripts on vellum, in the second century and later, made it much easier to do this sort of cross-book interpretation. Augustine was quite good at "flipping between passages." which was much more difficult when scrolls were used. In any case, use of types and prefigures was a common means of teaching throughout the first few centuries. It was only later that it was used less by the Protestants–perhaps as a reaction against earlier allegorical interpretation.
I want to suggest you get a copy of my book "From Shadow to Reality" (www.ipibooks.com) so that you can see more examples of the New Testament writers using the Old Testament as foreshadows. About your specific example, I do not believe that this particular foreshadowing–that the bread in the tabernacle is symbolic of Jesus is found in the New Testament. Of course, Jesus called himself the Bread of Life. I am very confident that the Jews thought of the bread in the tabernacle/temple, but Jesus did not make the specific connection, at least as recorded in the gospels.