Enable clippy::unnecessary_find_map (#8740)

This PR enables the
[`clippy::unnecessary_find_map`](https://rust-lang.github.io/rust-clippy/master/index.html#/unnecessary_find_map)
rule and fixes the outstanding violations.

Release Notes:

- N/A

tooling/xtask/src/main.rs

@@ -123,7 +123,6 @@ fn run_clippy(args: ClippyArgs) -> Result<()> {
         "clippy::suspicious_to_owned",
         "clippy::type_complexity",
         "clippy::unit_arg",
-        "clippy::unnecessary_find_map",
         "clippy::unnecessary_operation",
         "clippy::unnecessary_to_owned",
         "clippy::unnecessary_unwrap",