Restore nu_with_plugins test macro (#6065)

* Updated nu_with_plugins to handle new nushell

- Now it requires the plugin format and name to be passed in, because
  we can't really guess the format
- It calls `register` with format and plugin path
- It creates a temporary folder and in it an empty temporary plugin.nu
  so that the tests don't conflict with each other or with local copy of
  plugin.nu
- Instead of passing the commands via stdin it passes them via the new
  --commands command line argument

* Rename path to command for clarity

* Enable core_inc tests

Remove deprecated inc feature and replace with new plugin feature

* Update core_inc tests for new nu_with_plugins syntax

* Rework core_inc::can_only_apply_one

The new inc plugin doesn't error if passed more than one but instead
chooses the highest increment

* Gate all plugin tests behind feature = "plugin" instead of one by one

* Remove format!-like behavior from nu_with_plugins

nu_with_plugins had format!-like behavior where it would allow calls
such as this:
```rs
nu_with_plugins!(
  cwd: "dir/",
  "open {} | get {}",
  "Cargo.toml",
  "package.version"
)
```
And although nifty it seems to have never been used before and the same
can be achieved with a format! like so:
```rs
nu_with_plugins!(
  cwd: "dir/",
  format!("open {} | get {}", "Cargo.toml", "package.version")
)
```
So I am removing it to keep the complexity of the macro in check

* Add multi-plugin support to nu_with_plugins

Useful for testing interactions between plugins

* Alternative 1: run `cargo build` inside of tests

* Handle Windows by canonicalizing paths and add .exe

One VM install later and lots of learning about how command line
arguments work and here we are

tests/plugins/mod.rs

@@ -1,2 +1 @@
-#[cfg(features = "inc")]
 mod core_inc;