move dataframe commands to nu-cmd-dataframe (#9241)

All of the dataframe commands ported over with no issues...

### 11 tests are commented out (for now)

So 100 of the original 111 tests are passing with only 11 tests being
ignored for now..

As per our conversation in the core team meeting on Wednesday
I took @jntrnr  suggestion and just commented out the tests dealing
with
[IntoDatetime](https://github.com/nushell/nushell/blob/main/crates/nu-command/src/conversions/into/mod.rs)

Later on we can move this functionality out of nu-command if we decide
it makes sense...

### The following tests were ignored...

```rust
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_day.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_hour.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_minute.rs

modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_month.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_nanosecond.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_ordinal.rs

modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_second.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_week.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_weekday.rs

modified:   crates/nu-cmd-dataframe/src/dataframe/series/date/get_year.rs
modified:   crates/nu-cmd-dataframe/src/dataframe/series/string/strftime.rs
```

crates/nu-cmd-dataframe/src/dataframe/series/string/str_slice.rs

@@ -0,0 +1,110 @@
+use super::super::super::values::{Column, NuDataFrame};
+
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
+};
+use polars::prelude::{IntoSeries, Utf8NameSpaceImpl};
+
+#[derive(Clone)]
+pub struct StrSlice;
+
+impl Command for StrSlice {
+    fn name(&self) -> &str {
+        "dfr str-slice"
+    }
+
+    fn usage(&self) -> &str {
+        "Slices the string from the start position until the selected length."
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required("start", SyntaxShape::Int, "start of slice")
+            .named("length", SyntaxShape::Int, "optional length", Some('l'))
+            .input_type(Type::Custom("dataframe".into()))
+            .output_type(Type::Custom("dataframe".into()))
+            .category(Category::Custom("dataframe".into()))
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Creates slices from the strings",
+            example: "[abcded abc321 abc123] | dfr into-df | dfr str-slice 1 -l 2",
+            result: Some(
+                NuDataFrame::try_from_columns(vec![Column::new(
+                    "0".to_string(),
+                    vec![
+                        Value::test_string("bc"),
+                        Value::test_string("bc"),
+                        Value::test_string("bc"),
+                    ],
+                )])
+                .expect("simple df for test should not fail")
+                .into_value(Span::test_data()),
+            ),
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        command(engine_state, stack, call, input)
+    }
+}
+
+fn command(
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+    input: PipelineData,
+) -> Result<PipelineData, ShellError> {
+    let start: i64 = call.req(engine_state, stack, 0)?;
+
+    let length: Option<i64> = call.get_flag(engine_state, stack, "length")?;
+    let length = length.map(|v| v as u64);
+
+    let df = NuDataFrame::try_from_pipeline(input, call.head)?;
+    let series = df.as_series(call.head)?;
+
+    let chunked = series.utf8().map_err(|e| {
+        ShellError::GenericError(
+            "Error casting to string".into(),
+            e.to_string(),
+            Some(call.head),
+            Some("The str-slice command can only be used with string columns".into()),
+            Vec::new(),
+        )
+    })?;
+
+    let mut res = chunked.str_slice(start, length).map_err(|e| {
+        ShellError::GenericError(
+            "Error slicing series".into(),
+            e.to_string(),
+            Some(call.head),
+            None,
+            Vec::new(),
+        )
+    })?;
+    res.rename(series.name());
+
+    NuDataFrame::try_from_series(vec![res.into_series()], call.head)
+        .map(|df| PipelineData::Value(NuDataFrame::into_value(df, call.head), None))
+}
+
+#[cfg(test)]
+mod test {
+    use super::super::super::super::test_dataframe::test_dataframe;
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        test_dataframe(vec![Box::new(StrSlice {})])
+    }
+}