debugger: Improve step icons (#44017)

Closes https://github.com/zed-industries/zed/issues/38475

<img width="500" height="820" alt="Screenshot 2025-12-02 at 5  24@2x"
src="https://github.com/user-attachments/assets/802e4fd7-0d6d-4cc2-a77a-17df8c268fc7"
/>

Release Notes:

- N/A

assets/icons/debug_step_back.svg

@@ -1 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="none"><path stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M14 11.333A6 6 0 0 0 4 6.867l-1 .9"/><path stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.333" d="M2 4.667v4h4"/><path fill="#000" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M8 12a.667.667 0 1 0 0-1.333A.667.667 0 0 0 8 12Z"/></svg>

assets/icons/debug_step_into.svg

@@ -1 +1,5 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="none"><path stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M3.333 10 8 14.667 12.667 10M8 5.333v9.334"/><path fill="#000" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M8 2.667a.667.667 0 1 0 0-1.334.667.667 0 0 0 0 1.334Z"/></svg>
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M2 13H5" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M11 13H14" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M11.5 8.5L8 12M8 12L4.5 8.5M8 12L8 3" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>

assets/icons/debug_step_out.svg

@@ -1 +1,5 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="none"><path stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M3.333 6 8 1.333 12.667 6M8 10.667V1.333"/><path fill="#000" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M8 13.333a.667.667 0 1 1 0 1.334.667.667 0 0 1 0-1.334Z"/></svg>
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M4.5 6.5L8 3M8 3L11.5 6.5M8 3V12" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M2 13H5" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M11 13H14" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>

assets/icons/debug_step_over.svg

@@ -1 +1,5 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="none"><path stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M2 11.333a6 6 0 0 1 10-4.466l1 .9"/><path stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.333" d="M14 4.667v4h-4"/><path fill="#000" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.2" d="M8 12a.667.667 0 1 1 0-1.333A.667.667 0 0 1 8 12Z"/></svg>
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M2 11.333C2.00118 10.1752 2.33729 9.04258 2.96777 8.07159C3.59826 7.10059 4.49621 6.33274 5.55331 5.86064C6.61041 5.38853 7.78152 5.23235 8.9254 5.41091C10.0693 5.58947 11.1371 6.09516 12 6.86698L13 7.76698" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M14 4.66699V8.66699H10" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+<path d="M7 13H10" stroke="#C6CAD0" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>