Make example binaries proper cargo examples (#7019)

Should not be built by default with `cargo build`
Instead are compiled with `cargo test` to avoid bitrot
Run with `cargo run -p ... --example ...`

crates/nu-system/Cargo.toml

@@ -9,10 +9,6 @@ license = "MIT"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
-[[bin]]
-name = "ps"
-path = "src/main.rs"
-
 [dependencies]
 libc = "0.2"
 log = "0.4"

crates/nu-table/Cargo.toml

@@ -7,11 +7,6 @@ license = "MIT"
 name = "nu-table"
 version = "0.70.1"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-[[bin]]
-name = "table"
-path = "src/main.rs"
-
 [dependencies]
 nu-ansi-term = "0.46.0"
 nu-protocol = { path = "../nu-protocol", version = "0.70.1" }

crates/nu-term-grid/Cargo.toml

@@ -7,11 +7,6 @@ license = "MIT"
 name = "nu-term-grid"
 version = "0.70.1"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-[[bin]]
-name = "grid"
-path = "src/main.rs"
-
 [dependencies]
 unicode-width = "0.1.9"