Merge "Upgrade to nom-7." am: f8576eaeb6 am: 1ff204f380 am: 497e78cc06

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/cexpr/+/1840658

Change-Id: Idc6a5f8ae9f77b8b847f45a83df6c66cac91cc90