Reduced LOC by replacing several instances of Value::Int {}, Value::Float{}, Value::Bool {}, and Value::String {} with Value::int(), Value::float(), Value::boolean() and Value::string() (#7412)

# Description

While perusing Value.rs, I noticed the `Value::int()`, `Value::float()`,
`Value::boolean()` and `Value::string()` constructors, which seem
designed to make it easier to construct various Values, but which aren't
used often at all in the codebase. So, using a few find-replaces
regexes, I increased their usage. This reduces overall LOC because
structures like this:
```
Value::Int {
  val: a,
  span: head
}
```
are changed into
```
Value::int(a, head)
```
and are respected as such by the project's formatter.
There are little readability concerns because the second argument to all
of these is `span`, and it's almost always extremely obvious which is
the span at every callsite.

# User-Facing Changes

None.

# 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.

crates/nu-command/src/dataframe/expressions/as_nu.rs

@@ -32,14 +32,8 @@ impl Command for ExprAsNu {
             result: Some(Value::Record {
                 cols: vec!["expr".into(), "value".into()],
                 vals: vec![
-                    Value::String {
-                        val: "column".into(),
-                        span: Span::test_data(),
-                    },
-                    Value::String {
-                        val: "a".into(),
-                        span: Span::test_data(),
-                    },
+                    Value::string("column", Span::test_data()),
+                    Value::string("a", Span::test_data()),
                 ],
                 span: Span::test_data(),
             }),