Remove the NU_DISABLE_IR option (#14293)

# Description

Removes the `NU_DISABLE_IR` option and some code related to evaluating
blocks with the AST
evaluator.

Does not entirely remove the AST evaluator yet. We still have some
dependencies on expression
evaluation in a few minor places which will take a little bit of effort
to fix.

Also changes `debug profile` to always include instructions, because the
output is a little
confusing otherwise, and removes the different options for
instructions/exprs.

# User-Facing Changes

- `NU_DISABLE_IR` no longer has any effect, and is removed. There is no
way to use the AST
  evaluator.
- `debug profile` no longer has `--exprs`, `--instructions` options.
- `debug profile` lists `pc` and `instruction` columns by default now.

# Tests + Formatting

Eval tests fixed to only use IR.

# After Submitting

- [ ] release notes
- [ ] finish removing AST evaluator, come up with solutions for the
expression evaluation.

src/run.rs

@@ -26,9 +26,6 @@ pub(crate) fn run_commands(
     let ask_to_create_config = nu_path::nu_config_dir().map_or(false, |p| !p.exists());
 
     let mut stack = Stack::new();
-    if stack.has_env_var(engine_state, "NU_DISABLE_IR") {
-        stack.use_ir = false;
-    }
 
     // if the --no-config-file(-n) option is NOT passed, load the plugin file,
     // load the default env file or custom (depending on parsed_nu_cli_args.env_file),
@@ -119,10 +116,6 @@ pub(crate) fn run_file(
     trace!("run_file");
     let mut stack = Stack::new();
 
-    if stack.has_env_var(engine_state, "NU_DISABLE_IR") {
-        stack.use_ir = false;
-    }
-
     // if the --no-config-file(-n) option is NOT passed, load the plugin file,
     // load the default env file or custom (depending on parsed_nu_cli_args.env_file),
     // and maybe a custom config file (depending on parsed_nu_cli_args.config_file)
@@ -191,10 +184,6 @@ pub(crate) fn run_repl(
     let mut stack = Stack::new();
     let start_time = std::time::Instant::now();
 
-    if stack.has_env_var(engine_state, "NU_DISABLE_IR") {
-        stack.use_ir = false;
-    }
-
     if parsed_nu_cli_args.no_config_file.is_none() {
         setup_config(
             engine_state,

src/test_bins.rs

@@ -236,11 +236,6 @@ pub fn nu_repl() {
     engine_state.add_env_var("PWD".into(), Value::test_string(cwd.to_string_lossy()));
     engine_state.add_env_var("PATH".into(), Value::test_string(""));
 
-    // Disable IR in tests if set
-    if std::env::var_os("NU_DISABLE_IR").is_some() {
-        Arc::make_mut(&mut top_stack).use_ir = false;
-    }
-
     let mut last_output = String::new();
 
     load_standard_library(&mut engine_state).expect("Could not load the standard library.");