add raw-string literal support (#9956)

# Description

This PR adds raw string support by using `r#` at the beginning of single
quoted strings and `#` at the end.

Notice that escapes do not process, even within single quotes,
parentheses don't mean anything, $variables don't mean anything. It's
just a string.
```nushell
❯ echo r#'one\ntwo (blah) ($var)'#
one\ntwo (blah) ($var)
```
Notice how they work without `echo` or `print` and how they work without
carriage returns.
```nushell
❯ r#'adsfa'#
adsfa
❯ r##"asdfa'@qpejq'##
asdfa'@qpejq
❯ r#'asdfasdfasf
∙ foqwejfqo@'23rfjqf'#
```
They also have a special configurable color in the repl. (use single
quotes though)

![image](https://github.com/nushell/nushell/assets/343840/8780e21d-de4c-45b3-9880-2425f5fe10ef)

They should work like rust raw literals and allow `r##`, `r###`,
`r####`, etc, to help with having one or many `#`'s in the middle of
your raw-string.

They should work with `let` as well.

```nushell
r#'some\nraw\nstring'# | str upcase
```

closes https://github.com/nushell/nushell/issues/5091
# User-Facing Changes
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# Tests + Formatting
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- `cargo run -- -c "use std testing; testing run-tests --path
crates/nu-std"` to run the tests for the standard library

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---------

Co-authored-by: WindSoilder <WindSoilder@outlook.com>
Co-authored-by: Ian Manske <ian.manske@pm.me>

crates/nu-protocol/src/ast/expr.rs

@@ -36,6 +36,7 @@ pub enum Expr {
     Directory(String, bool),
     GlobPattern(String, bool),
     String(String),
+    RawString(String),
     CellPath(CellPath),
     FullCellPath(Box<FullCellPath>),
     ImportPattern(Box<ImportPattern>),
@@ -80,6 +81,7 @@ impl Expr {
             | Expr::ValueWithUnit(_)
             | Expr::DateTime(_)
             | Expr::String(_)
+            | Expr::RawString(_)
             | Expr::CellPath(_)
             | Expr::StringInterpolation(_)
             | Expr::Nothing => {

crates/nu-protocol/src/ast/expression.rs

@@ -279,6 +279,7 @@ impl Expression {
             }
             Expr::Signature(_) => false,
             Expr::String(_) => false,
+            Expr::RawString(_) => false,
             Expr::RowCondition(block_id) | Expr::Subexpression(block_id) => {
                 let block = working_set.get_block(*block_id);
 
@@ -436,6 +437,7 @@ impl Expression {
             }
             Expr::Signature(_) => {}
             Expr::String(_) => {}
+            Expr::RawString(_) => {}
             Expr::StringInterpolation(items) => {
                 for i in items {
                     i.replace_span(working_set, replaced, new_span)

crates/nu-protocol/src/debugger/profiler.rs

@@ -253,7 +253,7 @@ fn expr_to_string(engine_state: &EngineState, expr: &Expr) -> String {
         Expr::Record(_) => "record".to_string(),
         Expr::RowCondition(_) => "row condition".to_string(),
         Expr::Signature(_) => "signature".to_string(),
-        Expr::String(_) => "string".to_string(),
+        Expr::String(_) | Expr::RawString(_) => "string".to_string(),
         Expr::StringInterpolation(_) => "string interpolation".to_string(),
         Expr::Subexpression(_) => "subexpression".to_string(),
         Expr::Table(_) => "table".to_string(),

crates/nu-protocol/src/eval_base.rs

@@ -139,7 +139,7 @@ pub trait Eval {
                 Ok(Value::list(output_rows, expr.span))
             }
             Expr::Keyword(kw) => Self::eval::<D>(state, mut_state, &kw.expr),
-            Expr::String(s) => Ok(Value::string(s.clone(), expr.span)),
+            Expr::String(s) | Expr::RawString(s) => Ok(Value::string(s.clone(), expr.span)),
             Expr::Nothing => Ok(Value::nothing(expr.span)),
             Expr::ValueWithUnit(value) => match Self::eval::<D>(state, mut_state, &value.expr)? {
                 Value::Int { val, .. } => value.unit.item.build_value(val, value.unit.span),