Rust: Address result duplication in rust/hard-coded-cryptographic-value - #22426

Small fix for a result duplication issue in rust/hard-coded-cryptographic-value. The issue is a match expression containing constants in each or many of the match arms, for example (from the test):

let str3 = match(val) {
    0 => "one", // constant
    1 => "two", // constant
    _ => "many" // constant
}

It turns out this can cause quite severe multiplication of results in rare cases (e.g. imagine the above but with 100 cases, and flowing to 20 sinks). The solution is to make the match expression itself the source, as it's close enough to see what's going on with just one result.