feat(where): Support stored closure (#15697)

# Description

- `where` used to be able to filter using stored closures at some point
using a flag.
  > #5955
- This was later removed and `filter` command added to cover the use
case.
  > #7365

This PR once again allows using `where` with closures stored in
variables.

```nushell
let cond = { $in mod 2 == 0 }
1..10 | where $cond
# => ╭───┬────╮
# => │ 0 │  2 │
# => │ 1 │  4 │
# => │ 2 │  6 │
# => │ 3 │  8 │
# => │ 4 │ 10 │
# => ╰───┴────╯

let nested = {cond: { $in mod 2 == 0 }}
1..10 | where $nested.cond 
# => ╭───┬────╮
# => │ 0 │  2 │
# => │ 1 │  4 │
# => │ 2 │  6 │
# => │ 3 │  8 │
# => │ 4 │ 10 │
# => ╰───┴────╯
``` 

This does not interfere with using `$it` or one of its fields as the
condition.
```nushell
[[name state]; [foo true] [bar false] [baz true] [quox false]]
| where $it.state
# => ╭───┬──────┬───────╮
# => │ # │ name │ state │
# => ├───┼──────┼───────┤
# => │ 0 │ foo  │ true  │
# => │ 1 │ baz  │ true  │
# => ╰───┴──────┴───────╯
``` 

This change obsoletes `filter`, deprecate it in the future?

# User-Facing Changes

# Tests + Formatting

Added examples and tests.

- 🟢 toolkit fmt
- 🟢 toolkit clippy
- 🟢 toolkit test
- 🟢 toolkit test stdlib


# After Submitting

---------

Co-authored-by: Bahex <17417311+Bahex@users.noreply.github.com>

crates/nu-parser/src/parser.rs

@@ -3609,6 +3609,16 @@ pub fn parse_row_condition(working_set: &mut StateWorkingSet, spans: &[Span]) ->
     let block_id = match expression.expr {
         Expr::Block(block_id) => block_id,
         Expr::Closure(block_id) => block_id,
+        Expr::FullCellPath(ref box_fcp) if box_fcp.head.as_var().is_some_and(|id| id != var_id) => {
+            let mut expression = expression;
+            expression.ty = Type::Any;
+            return expression;
+        }
+        Expr::Var(arg_var_id) if arg_var_id != var_id => {
+            let mut expression = expression;
+            expression.ty = Type::Any;
+            return expression;
+        }
         _ => {
             // We have an expression, so let's convert this into a block.
             let mut block = Block::new();