Consider using cargo-generate for Linera project command.

[deuszx]

          Probably not blocking, since this isn't new to this PR, but I think that we could replace these functions with a call to [`cargo-generate`](https://github.com/cargo-generate/cargo-generate).  It [supports being called as a library](https://github.com/cargo-generate/cargo-generate/blob/main/examples/how-to-use-cargo-gen-as-library/src/main.rs) and handles all the substitution for you — complete with a nice developer flow where it prompts for information that isn't provided.

Originally posted by @Twey in #2578 (comment)