Update internal use of decimal to float (#10333)

# Description
We made the decision that our floating point type should be referred to
as `float` over `decimal`.
Commands were updated by #9979 and #10320

Now make the internal codebase consistent in referring to this data type
as `float`.

Work for #10332

# User-Facing Changes

`decimal` has been removed as a type name/symbol. 

Instead of 
```nushell
def foo [bar: decimal] decimal -> decimal {}
```
use 
```nushell
def foo [bar: float] float -> float {}
```

Potential effect of `SyntaxShape`'s `Display` implementation now also
referring to `float` instead of `decimal`

# Details
- Rename `SyntaxShape::Decimal` to `Float`
- Update `Display for SyntaxShape` to `float`
- Update error message + fn name in dataframe code
- Fix docs in command examples
- Rename tests that are float specific
- Update doccomment on `SyntaxShape`
- Update comment in script

# Tests + Formatting
Updates the names of some tests

crates/nu-command/src/conversions/into/binary.rs

@@ -107,7 +107,7 @@ impl Command for SubCommand {
                 result: None,
             },
             Example {
-                description: "convert a decimal to a nushell binary primitive",
+                description: "convert a float to a nushell binary primitive",
                 example: "1.234 | into binary",
                 result: Some(Value::binary(
                     1.234f64.to_ne_bytes().to_vec(),

crates/nu-command/src/conversions/into/bool.rs

@@ -95,12 +95,12 @@ impl Command for SubCommand {
                 result: Some(Value::bool(true, span)),
             },
             Example {
-                description: "convert decimal to boolean",
+                description: "convert float to boolean",
                 example: "0.3 | into bool",
                 result: Some(Value::bool(true, span)),
             },
             Example {
-                description: "convert decimal string to boolean",
+                description: "convert float string to boolean",
                 example: "'0.0' | into bool",
                 result: Some(Value::bool(false, span)),
             },

crates/nu-command/src/conversions/into/filesize.rs

@@ -105,7 +105,7 @@ impl Command for SubCommand {
                 result: Some(Value::filesize(2, Span::test_data())),
             },
             Example {
-                description: "Convert decimal to filesize",
+                description: "Convert float to filesize",
                 example: "8.3 | into filesize",
                 result: Some(Value::filesize(8, Span::test_data())),
             },

crates/nu-command/src/conversions/into/float.rs

@@ -145,7 +145,7 @@ mod tests {
 
     #[test]
     #[allow(clippy::approx_constant)]
-    fn string_to_decimal() {
+    fn string_to_float() {
         let word = Value::test_string("3.1415");
         let expected = Value::test_float(3.1415);
 
@@ -154,7 +154,7 @@ mod tests {
     }
 
     #[test]
-    fn communicates_parsing_error_given_an_invalid_decimallike_string() {
+    fn communicates_parsing_error_given_an_invalid_floatlike_string() {
         let invalid_str = Value::test_string("11.6anra");
 
         let actual = action(

crates/nu-command/src/conversions/into/int.rs

@@ -169,7 +169,7 @@ impl Command for SubCommand {
                 result: Some(Value::test_int(2)),
             },
             Example {
-                description: "Convert decimal to integer",
+                description: "Convert float to integer",
                 example: "5.9 | into int",
                 result: Some(Value::test_int(5)),
             },

crates/nu-command/src/conversions/into/string.rs

@@ -89,22 +89,22 @@ impl Command for SubCommand {
                 result: Some(Value::test_string("5.000")),
             },
             Example {
-                description: "convert decimal to string and round to nearest integer",
+                description: "convert float to string and round to nearest integer",
                 example: "1.7 | into string -d 0",
                 result: Some(Value::test_string("2")),
             },
             Example {
-                description: "convert decimal to string",
+                description: "convert float to string",
                 example: "1.7 | into string -d 1",
                 result: Some(Value::test_string("1.7")),
             },
             Example {
-                description: "convert decimal to string and limit to 2 decimals",
+                description: "convert float to string and limit to 2 decimals",
                 example: "1.734 | into string -d 2",
                 result: Some(Value::test_string("1.73")),
             },
             Example {
-                description: "try to convert decimal to string and provide negative decimal points",
+                description: "try to convert float to string and provide negative decimal points",
                 example: "1.734 | into string -d -2",
                 result: None,
                 // FIXME
@@ -116,7 +116,7 @@ impl Command for SubCommand {
                 // }),
             },
             Example {
-                description: "convert decimal to string",
+                description: "convert float to string",
                 example: "4.3 | into string",
                 result: Some(Value::test_string("4.3")),
             },