Restrict closure expression to be something like {|| ...} (#8290)

# Description

As title, closes: #7921 closes: #8273

# User-Facing Changes

when define a closure without pipe, nushell will raise error for now:
```
❯ let x = {ss ss}
Error: nu::parser::closure_missing_pipe

  × Missing || inside closure
   ╭─[entry #2:1:1]
 1 │ let x = {ss ss}
   ·         ───┬───
   ·            ╰── Parsing as a closure, but || is missing
   ╰────
  help: Try add || to the beginning of closure
```

`any`, `each`, `all`, `where` command accepts closure, it forces user
input closure like `{||`, or parse error will returned.
```
❯ {major:2, minor:1, patch:4} | values | each { into string }
Error: nu::parser::closure_missing_pipe

  × Missing || inside closure
   ╭─[entry #4:1:1]
 1 │ {major:2, minor:1, patch:4} | values | each { into string }
   ·                                             ───────┬───────
   ·                                                    ╰── Parsing as a closure, but || is missing
   ╰────
  help: Try add || to the beginning of closure
```

`with-env`, `do`, `def`, `try` are special, they still remain the same,
although it says that it accepts a closure, but they don't need to be
written like `{||`, it's more likely a block but can capture variable
outside of scope:
```
❯ def test [input] { echo [0 1 2] | do { do { echo $input } } }; test aaa
aaa
```

Just realize that It's a big breaking change, we need to update config
and scripts...

# Tests + Formatting

Don't forget to add tests that cover your changes.

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

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

src/tests/test_engine.rs

@@ -115,7 +115,7 @@ fn proper_variable_captures() -> TestResult {
 #[test]
 fn proper_variable_captures_with_calls() -> TestResult {
     run_test(
-        r#"def foo [] { let y = 60; def bar [] { $y }; { bar } }; do (foo)"#,
+        r#"def foo [] { let y = 60; def bar [] { $y }; {|| bar } }; do (foo)"#,
         "60",
     )
 }
@@ -329,7 +329,10 @@ fn default_value_expression() -> TestResult {
 
 #[test]
 fn loose_each() -> TestResult {
-    run_test(r#"[[1, 2, 3], [4, 5, 6]] | each { $in.1 } | math sum"#, "7")
+    run_test(
+        r#"[[1, 2, 3], [4, 5, 6]] | each {|| $in.1 } | math sum"#,
+        "7",
+    )
 }
 
 #[test]
@@ -340,7 +343,7 @@ fn in_means_input() -> TestResult {
 #[test]
 fn in_iteration() -> TestResult {
     run_test(
-        r#"[3, 4, 5] | each { echo $"hi ($in)" } | str join"#,
+        r#"[3, 4, 5] | each {|| echo $"hi ($in)" } | str join"#,
         "hi 3hi 4hi 5",
     )
 }