Update and refine some icons (#35938)

Follow up to https://github.com/zed-industries/zed/pull/35856.

Release Notes:

- N/A

assets/icons/blocks.svg

@@ -1 +1,3 @@
-<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="1.5" d="M12.429 2H9.57A.571.571 0 0 0 9 2.571V5.43c0 .315.256.571.571.571h2.858A.571.571 0 0 0 13 5.429V2.57A.571.571 0 0 0 12.429 2ZM6.5 13V4.643A.643.643 0 0 0 5.857 4H2.643A.643.643 0 0 0 2 4.643v7.714a.643.643 0 0 0 .643.643h7.714a.643.643 0 0 0 .643-.643V9.143a.643.643 0 0 0-.643-.643H2"/></svg>
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M7 13.5V5.143C7 4.97247 6.93226 4.80892 6.81167 4.68833C6.69108 4.56774 6.52753 4.5 6.357 4.5H3.143C2.97247 4.5 2.80892 4.56774 2.68833 4.68833C2.56774 4.80892 2.5 4.97247 2.5 5.143V12.857C2.5 12.9414 2.51663 13.0251 2.54895 13.1031C2.58126 13.1811 2.62862 13.252 2.68833 13.3117C2.74804 13.3714 2.81892 13.4187 2.89693 13.4511C2.97495 13.4834 3.05856 13.5 3.143 13.5H10.857C10.9414 13.5 11.0251 13.4834 11.1031 13.4511C11.1811 13.4187 11.252 13.3714 11.3117 13.3117C11.3714 13.252 11.4187 13.1811 11.4511 13.1031C11.4834 13.0251 11.5 12.9414 11.5 12.857V9.643C11.5 9.47247 11.4323 9.30892 11.3117 9.18833C11.1911 9.06774 11.0275 9 10.857 9H2.5M12.929 2.5H10.07C9.91873 2.50026 9.77376 2.56054 9.66689 2.6676C9.56002 2.77465 9.5 2.91973 9.5 3.071V5.93C9.5 6.245 9.756 6.501 10.071 6.501H12.929C13.0041 6.501 13.0784 6.4862 13.1477 6.45744C13.2171 6.42868 13.2801 6.38653 13.3331 6.3334C13.3861 6.28028 13.4282 6.21721 13.4568 6.14782C13.4855 6.07843 13.5001 6.00407 13.5 5.929V3.07C13.4997 2.91873 13.4395 2.77376 13.3324 2.66689C13.2254 2.56002 13.0803 2.5 12.929 2.5Z" stroke="black" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>