Remove default features when fullstack is enabled and one platform is enabled in the default features

[ealmloff]

When you have a cargo.toml like this:

[dependencies]
dioxus = { version = "0.6.3", features = ["fullstack"] }

[features]
default = ["web"]
web = ["dioxus/web"]
server = ["dioxus/server"]

The CLI currently tries to include the web feature in your server build which can cause unexpected behavior. This PR fixes that issue and adds a regression test

Closes #3740
Closes #3491