Benchmark each pipeline element (#7854)

# Description

Adds a `profile` command that profiles each pipeline element of a block
and can also recursively step into child blocks.

# Limitations
* It is implemented using pipeline metadata which currently get lost in
some circumstances (e.g.,
https://github.com/nushell/nushell/issues/4501). This means that the
profiler will lose data coming from subexpressions. This issue will
hopefully be solved in the future.
* It also does not step into individual loop iteration which I'm not
sure why but maybe that's a good thing.

# User-Facing Changes

Shouldn't change any existing behavior.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

---------

Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>

crates/nu-protocol/src/engine/stack.rs

@@ -7,6 +7,44 @@ use crate::{ShellError, Span, Value, VarId};
 /// Environment variables per overlay
 pub type EnvVars = HashMap<String, HashMap<String, Value>>;
 
+#[derive(Debug, Clone)]
+pub struct ProfilingConfig {
+    pub max_depth: i64,
+    pub depth: i64,
+    pub collect_source: bool,
+    pub collect_values: bool,
+}
+
+impl ProfilingConfig {
+    pub fn new(max_depth: i64, collect_source: bool, collect_values: bool) -> Self {
+        ProfilingConfig {
+            max_depth,
+            depth: 0,
+            collect_source,
+            collect_values,
+        }
+    }
+
+    pub fn enter_block(&mut self) {
+        self.depth += 1;
+    }
+
+    pub fn leave_block(&mut self) {
+        self.depth -= 1;
+    }
+
+    pub fn should_debug(&self) -> bool {
+        self.depth <= self.max_depth
+    }
+
+    pub fn reset(&mut self) {
+        self.max_depth = 0;
+        self.depth = 0;
+        self.collect_source = false;
+        self.collect_values = false;
+    }
+}
+
 /// A runtime value stack used during evaluation
 ///
 /// A note on implementation:
@@ -35,6 +73,7 @@ pub struct Stack {
     /// List of active overlays
     pub active_overlays: Vec<String>,
     pub recursion_count: Box<u64>,
+    pub profiling_config: ProfilingConfig,
 }
 
 impl Stack {
@@ -45,6 +84,7 @@ impl Stack {
             env_hidden: HashMap::new(),
             active_overlays: vec![DEFAULT_OVERLAY_NAME.to_string()],
             recursion_count: Box::new(0),
+            profiling_config: ProfilingConfig::new(0, false, false),
         }
     }
 
@@ -126,6 +166,7 @@ impl Stack {
             env_hidden: HashMap::new(),
             active_overlays: self.active_overlays.clone(),
             recursion_count: self.recursion_count.to_owned(),
+            profiling_config: self.profiling_config.clone(),
         }
     }
 
@@ -151,6 +192,7 @@ impl Stack {
             env_hidden: HashMap::new(),
             active_overlays: self.active_overlays.clone(),
             recursion_count: self.recursion_count.to_owned(),
+            profiling_config: self.profiling_config.clone(),
         }
     }