feature: add the standard library tests to the PR template and the toolkit (#8629)

Related to #8525.

# Description
With #8525, the tests for the standard library have been enabled in the
CI.
The only places where these tests are missing are
- the PR template
- the toolkit

This PR adds
- `cargo run -- crates/nu-utils/standard_library/tests.nu` to the PR
template
- the same command as `toolkit test stdlib`
- the `test stdlib` command to `toolkit check pr`

# User-Facing Changes
```
$nothing
```

# Tests + Formatting
the new output of `toolkit check pr`, with the same color code:
> - 🟢 `toolkit fmt`
> - 🟢 `toolkit clippy`
> - 🟢 `toolkit test`
> - 🟢 `toolkit test stdlib`

# After Submitting
```
$nothing
```

.github/pull_request_template.md

@@ -18,6 +18,7 @@ Make sure you've run and fixed any issues with these commands:
 - `cargo fmt --all -- --check` to check standard code formatting (`cargo fmt --all` applies these changes)
 - `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A clippy::needless_collect` to check that you're using the standard code style
 - `cargo test --workspace` to check that all tests pass
+- `cargo run -- crates/nu-utils/standard_library/tests.nu` to run the tests for the standard library
 
 > **Note**
 > from `nushell` you can also use the `toolkit` as follows

toolkit.nu

@@ -35,6 +35,11 @@ export def test [
     }
 }
 
+# run the tests for the standard library
+export def "test stdlib" [] {
+    cargo run -- crates/nu-utils/standard_library/tests.nu
+}
+
 # print the pipe input inside backticks, dimmed and italic, as a pretty command
 def pretty-print-command [] {
     $"`(ansi default_dimmed)(ansi default_italic)($in)(ansi reset)`"
@@ -53,15 +58,18 @@ def report [
     --fail-fmt: bool
     --fail-clippy: bool
     --fail-test: bool
+    --fail-test-stdlib: bool
     --no-fail: bool
 ] {
-    [fmt clippy test] | wrap stage
+    [fmt clippy test "test stdlib"]
+    | wrap stage
     | merge (
-        if $no_fail          { [true     true     true] }
-        else if $fail_fmt    { [false    $nothing $nothing] }
-        else if $fail_clippy { [true     false    $nothing] }
-        else if $fail_test   { [true     true     false] }
-        else                 { [$nothing $nothing $nothing] }
+        if $no_fail               { [true     true     true     true] }
+        else if $fail_fmt         { [false    $nothing $nothing $nothing] }
+        else if $fail_clippy      { [true     false    $nothing $nothing] }
+        else if $fail_test        { [true     true     false    $nothing] }
+        else if $fail_test_stdlib { [true     true     true     false] }
+        else                      { [$nothing $nothing $nothing $nothing] }
         | wrap success
     )
     | upsert emoji {|it|
@@ -194,5 +202,12 @@ export def "check pr" [
         return (report --fail-test)
     }
 
+    print $"running ('toolkit test stdlib' | pretty-print-command)"
+    try {
+        test stdlib
+    } catch {
+        return (report --fail-test-stdlib)
+    }
+
     report --no-fail
 }