Add metadata files for itertools. am: 20d7a6fa89 am: a3fb21f89d am: dac361d45c

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/itertools/+/1621382

Change-Id: I993d661354816deca9176e4d3ab285cc2a45a4b2