Embed things in juliainstaller

[davidanthoff]

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.