Fix incorrect handling of boolean flags for builtin commands (#11492)

# Description
Possible fix of #11456
This PR fixes a bug where builtin commands did not respect the logic of
dynamically passed boolean flags. The reason is
[has_flag](6f59abaf43/crates/nu-protocol/src/ast/call.rs (L204C5-L212C6))
method did not evaluate and take into consideration expression used with
flag.

To address this issue a solution is proposed:
1. `has_flag` method is moved to `CallExt` and new logic to evaluate
expression and check if it is a boolean value is added
2. `has_flag_const` method is added to `CallExt` which is a constant
version of `has_flag`
3. `has_named` method is added to `Call` which is basically the old
logic of `has_flag`
4. All usages of `has_flag` in code are updated, mostly to pass
`engine_state` and `stack` to new `has_flag`. In `run_const` commands it
is replaced with `has_flag_const`. And in a few select places: parser,
`to nuon` and `into string` old logic via `has_named` is used.

# User-Facing Changes
Explicit values of boolean flags are now respected in builtin commands.
Before:

![image](https://github.com/nushell/nushell/assets/17511668/f9fbabb2-3cfd-43f9-ba9e-ece76d80043c)
After:

![image](https://github.com/nushell/nushell/assets/17511668/21867596-2075-437f-9c85-45563ac70083)

Another example:
Before:

![image](https://github.com/nushell/nushell/assets/17511668/efdbc5ca-5227-45a4-ac5b-532cdc2bbf5f)
After:

![image](https://github.com/nushell/nushell/assets/17511668/2907d5c5-aa93-404d-af1c-21cdc3d44646)


# Tests + Formatting
Added test reproducing some variants of original issue.

crates/nu-command/src/strings/char_.rs

@@ -229,7 +229,7 @@ impl Command for Char {
     ) -> Result<PipelineData, ShellError> {
         let call_span = call.head;
         // handle -l flag
-        if call.has_flag("list") {
+        if call.has_flag(engine_state, stack, "list")? {
             return Ok(CHAR_MAP
                 .iter()
                 .map(move |(name, s)| {
@@ -251,7 +251,7 @@ impl Command for Char {
                 .into_pipeline_data(engine_state.ctrlc.clone()));
         }
         // handle -u flag
-        if call.has_flag("integer") {
+        if call.has_flag(engine_state, stack, "integer")? {
             let args: Vec<i64> = call.rest(engine_state, stack, 0)?;
             if args.is_empty() {
                 return Err(ShellError::MissingParameter {
@@ -268,7 +268,7 @@ impl Command for Char {
                 multi_byte.push(integer_to_unicode_char(arg, span)?)
             }
             Ok(Value::string(multi_byte, call_span).into_pipeline_data())
-        } else if call.has_flag("unicode") {
+        } else if call.has_flag(engine_state, stack, "unicode")? {
             let args: Vec<String> = call.rest(engine_state, stack, 0)?;
             if args.is_empty() {
                 return Err(ShellError::MissingParameter {