Embed things in juliainstaller

Once the scenario in https://zameermanji.com/blog/2021/6/17/embedding-a-rust-binary-in-another-rust-binary/ is easier to achieve (i.e. once upstream cargo supports these conditional compiles better) we should embed `julialauncher` and `juliaup` inside the `juliainstaller` binary itself.

Other helpful links: https://doc.rust-lang.org/std/macro.include_bytes.html and https://github.com/pyros2097/rust-embed.

Start with the linked article on embedding a Rust binary, then review Rust's include_bytes! documentation and rust-embed. Done means julialauncher and juliaup are embedded inside the juliainstaller binary once upstream Cargo supports the required conditional compiles.

Written by the indexing model from the issue text.