Move branding and package install into cargo-run (#4266)

* Move branding asset fetch into cargo-run

* Move frontend npm install into cargo-run

* Rename branding::ensure to branding::setup

* Wording nits

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Co-authored-by: Keavon Chambers <keavon@keavon.com>

tools/cargo-run/src/lib.rs

@@ -1,5 +1,6 @@
 use std::path::PathBuf;
 
+pub mod branding;
 pub mod cmd;
 pub mod frontend;
 pub mod requirements;