Coerce boolean values into strings too (#14704)

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# Description
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The `Value::coerce_str` method weirdly doesn't allow coercing boolean
values into strings while commands like `true | into string` work
without issues. So I added that.

# User-Facing Changes
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helps us keep track of breaking changes. -->

This is technically a breaking change if a nushell library user depended
on the fact that boolean values weren't coerceable to strings. But I
doubt that really.

# Tests + Formatting
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crates/nu-protocol/src/value/mod.rs

@@ -366,6 +366,7 @@ impl Value {
     /// Returns this `Value` converted to a `str` or an error if it cannot be converted
     ///
     /// Only the following `Value` cases will return an `Ok` result:
+    /// - `Bool`
     /// - `Int`
     /// - `Float`
     /// - `String`
@@ -379,7 +380,8 @@ impl Value {
     ///     assert_eq!(
     ///         matches!(
     ///             val,
-    ///             Value::Int { .. }
+    ///             Value::Bool { .. }
+    ///                 | Value::Int { .. }
     ///                 | Value::Float { .. }
     ///                 | Value::String { .. }
     ///                 | Value::Glob { .. }
@@ -392,6 +394,7 @@ impl Value {
     /// ```
     pub fn coerce_str(&self) -> Result<Cow<str>, ShellError> {
         match self {
+            Value::Bool { val, .. } => Ok(Cow::Owned(val.to_string())),
             Value::Int { val, .. } => Ok(Cow::Owned(val.to_string())),
             Value::Float { val, .. } => Ok(Cow::Owned(val.to_string())),
             Value::String { val, .. } => Ok(Cow::Borrowed(val)),
@@ -419,6 +422,7 @@ impl Value {
     /// if you do not need to keep the original `Value` around.
     ///
     /// Only the following `Value` cases will return an `Ok` result:
+    /// - `Bool`
     /// - `Int`
     /// - `Float`
     /// - `String`
@@ -432,7 +436,8 @@ impl Value {
     ///     assert_eq!(
     ///         matches!(
     ///             val,
-    ///             Value::Int { .. }
+    ///             Value::Bool { .. }
+    ///                 | Value::Int { .. }
     ///                 | Value::Float { .. }
     ///                 | Value::String { .. }
     ///                 | Value::Glob { .. }
@@ -450,6 +455,7 @@ impl Value {
     /// Returns this `Value` converted to a `String` or an error if it cannot be converted
     ///
     /// Only the following `Value` cases will return an `Ok` result:
+    /// - `Bool`
     /// - `Int`
     /// - `Float`
     /// - `String`
@@ -463,7 +469,8 @@ impl Value {
     ///     assert_eq!(
     ///         matches!(
     ///             val,
-    ///             Value::Int { .. }
+    ///             Value::Bool { .. }
+    ///                 | Value::Int { .. }
     ///                 | Value::Float { .. }
     ///                 | Value::String { .. }
     ///                 | Value::Glob { .. }
@@ -477,6 +484,7 @@ impl Value {
     pub fn coerce_into_string(self) -> Result<String, ShellError> {
         let span = self.span();
         match self {
+            Value::Bool { val, .. } => Ok(val.to_string()),
             Value::Int { val, .. } => Ok(val.to_string()),
             Value::Float { val, .. } => Ok(val.to_string()),
             Value::String { val, .. } => Ok(val),