Update install instructions of the stellar-cli

[leighmcculloch]

What

Update install instructions of the stellar-cli:

• Remove cargo-binstall instructions
• Elevate binary installs over source
• Remove instructions for installing from the repo

Why

• Remove cargo-binstall instructions

• It breaks from time to time.
• It's broken right now.
• It installs from source without --locked which is not secure.
• The tool doesn't verify github attestations, vs brew that does.
• Issues about improving supply chain vulnerability are getting little attention.

• Elevate binary installs over source

• Building from source is time consuming and requires more than the rust compiler to be installed.
• Building from source requires a significant amount of system resources.
• Most folks will have a better experience installing a precompiled binary.

• Remove instructions for installing from the repo

• 99% of devs should be installing the latest release.
• We're releasing more frequently lately and getting features out fast.

---

We still have a gap installing binaries for Windows, but we're on it and that is being tracked in:

• Make installing binary releases a native experience stellar-cli#1446

---

Note that related to this, I've opened an issue on the stellar-cli repo to fix the issues above that are within our control. The change to the docs is because I don't think we should be pushing it as a preferred way to install ahead of other things like homebrew which has more attention to supply chain security.

• cargo-binstall release install broken stellar-cli#1678

[stellar-jenkins]

Preview is available here:
http://developers-pr1045.previews.kube001.services.stellar-ops.com