replace regex crate with fancy_regex (#14646)

# Description

We removed the regex crate long ago but there were a few instances where
we could not remove it because fancy-regex did not have a split/splitn,
and maybe other functions. Those functions now exist in the latest
fancy-regex crate so we can now remove it.
 
# User-Facing Changes
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crates/nu-command/src/strings/split/column.rs

@@ -1,7 +1,6 @@
+use fancy_regex::{escape, Regex};
 use nu_engine::command_prelude::*;
 
-use regex::Regex;
-
 #[derive(Clone)]
 pub struct SubCommand;
 
@@ -182,7 +181,7 @@ fn split_column(
     let regex = if args.has_regex {
         Regex::new(&args.separator.item)
     } else {
-        let escaped = regex::escape(&args.separator.item);
+        let escaped = escape(&args.separator.item);
         Regex::new(&escaped)
     }
     .map_err(|e| ShellError::GenericError {
@@ -220,10 +219,12 @@ fn split_column_helper(
         let split_result: Vec<_> = match max_split {
             Some(max_split) => separator
                 .splitn(&s, max_split)
+                .filter_map(|x| x.ok())
                 .filter(|x| !(collapse_empty && x.is_empty()))
                 .collect(),
             None => separator
                 .split(&s)
+                .filter_map(|x| x.ok())
                 .filter(|x| !(collapse_empty && x.is_empty()))
                 .collect(),
         };

crates/nu-command/src/strings/split/list.rs

@@ -1,7 +1,6 @@
+use fancy_regex::Regex;
 use nu_engine::command_prelude::*;
 
-use regex::Regex;
-
 #[derive(Clone)]
 pub struct SubCommand;
 
@@ -193,7 +192,7 @@ impl Matcher {
         Ok(match self {
             Matcher::Regex(regex) => {
                 if let Ok(rhs_str) = rhs.coerce_str() {
-                    regex.is_match(&rhs_str)
+                    regex.is_match(&rhs_str).unwrap_or(false)
                 } else {
                     false
                 }

crates/nu-command/src/strings/split/row.rs

@@ -1,7 +1,6 @@
+use fancy_regex::{escape, Regex};
 use nu_engine::command_prelude::*;
 
-use regex::Regex;
-
 #[derive(Clone)]
 pub struct SubCommand;
 
@@ -158,7 +157,7 @@ fn split_row(
     let regex = if args.has_regex {
         Regex::new(&args.separator.item)
     } else {
-        let escaped = regex::escape(&args.separator.item);
+        let escaped = escape(&args.separator.item);
         Regex::new(&escaped)
     }
     .map_err(|e| ShellError::GenericError {
@@ -187,11 +186,35 @@ fn split_row_helper(v: &Value, regex: &Regex, max_split: Option<usize>, name: Sp
                 match max_split {
                     Some(max_split) => regex
                         .splitn(&s, max_split)
-                        .map(|x: &str| Value::string(x, v_span))
+                        .map(|x| match x {
+                            Ok(val) => Value::string(val, v_span),
+                            Err(err) => Value::error(
+                                ShellError::GenericError {
+                                    error: "Error with regular expression".into(),
+                                    msg: err.to_string(),
+                                    span: Some(v_span),
+                                    help: None,
+                                    inner: vec![],
+                                },
+                                v_span,
+                            ),
+                        })
                         .collect(),
                     None => regex
                         .split(&s)
-                        .map(|x: &str| Value::string(x, v_span))
+                        .map(|x| match x {
+                            Ok(val) => Value::string(val, v_span),
+                            Err(err) => Value::error(
+                                ShellError::GenericError {
+                                    error: "Error with regular expression".into(),
+                                    msg: err.to_string(),
+                                    span: Some(v_span),
+                                    help: None,
+                                    inner: vec![],
+                                },
+                                v_span,
+                            ),
+                        })
                         .collect(),
                 }
             } else {