feat: Produce graph of internal Barretenberg dependencies (#4225)

The graph is directed, with $A\to B$ meaning that $A$ depends on $B$.
Result:

![barretenberg_modules](https://github.com/AztecProtocol/aztec-packages/assets/26756572/5bc0745a-1b14-431f-9059-16e4b6b4a217)
A follow on could rewrite the CMakeLists.txt files to actually make use
of this minimal representation of dependencies, but that feels
unnecessary at the moment.

barretenberg/cpp/.gitignore

@@ -9,3 +9,5 @@ CMakeUserPresets.json
 acir_tests
 # we may download go in scripts/collect_heap_information.sh
 go*.tar.gz
+barretenberg_modules.dot
+barretenberg_modules.png

barretenberg/cpp/scripts/barretenberg_module_digraph.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -eu
+
+TMP=tmp.dot
+RESULT_DOT=barretenberg_modules.dot
+RESULT_PNG=barretenberg_modules.png
+
+# initialize a directed graph for graphviz
+echo digraph BarretenbergModules { > $TMP
+# populate the directed graph
+for file in $(find ./src/barretenberg/ -iname CMakeLists.txt); do
+  opening_chars=$(head -c 19 "$file")
+    if [ "$opening_chars" == barretenberg_module ]; then
+      awk -f ./scripts/barretenberg_module_digraph_edges.awk $file >> $TMP
+    fi
+done
+echo } >> $TMP
+
+# apply transitive reduction to remove dependcies that are implied by other dependencies
+cat $TMP | tred > $RESULT_DOT
+rm $TMP
+
+# produce a PNG of the graph
+dot -Tpng $RESULT_DOT -o $RESULT_PNG

barretenberg/cpp/scripts/barretenberg_module_digraph_edges.awk

@@ -0,0 +1,35 @@
+# Function to extract words between parentheses
+function extract_edges(line) {
+    match(line, /\(.*\)/);  # Find the portion within parentheses
+    line = substr(line, RSTART + 1, RLENGTH - 2);  # Extract the words
+    gsub(/^[ ]+/, "", line); # Remove leading spaces and tabs
+    gsub(/[ ]+$/, "", line); # Remove trailing spaces and tabs
+    gsub(/[ ]+/, " ", line); # Sub multiple spaces for a single space
+    split(line, modules, " "); # Split into an array of words
+
+    # If node has no dependencies, just add the node
+    if (length(modules)==1) {
+        print modules[1];
+    }
+    else { # add edges
+        for (i = 2; i <= length(modules); i++) {
+            print modules[1]" -> "modules[i];
+        }
+    }
+}
+
+# Main AWK script
+{
+    # Concatenate lines if the opening parenthesis is not closed
+    while (!/\)/) {
+        current_line = $0;
+        getline;
+        $0 = current_line $0;
+    }
+
+    # Check if the line begins with "barretenberg_module". If so, extact the digraph edges
+     function_name = "barretenberg_module";
+    if ($0 ~ "^" function_name "\\(") {
+        extract_edges($0);
+    }
+}