Revise and clean up some icons (#35582)

This is really just a small beginning, as there are many other icons to
be revised and cleaned up. Our current set is a bit of a mess in terms
of dimension, spacing, stroke width, and terminology. I'm sure there are
more non-used icons I'm not covering here, too. We'll hopefully tackle
it all soon leading up to 1.0.

Closes https://github.com/zed-industries/zed/issues/35576

Release Notes:

- N/A

assets/icons/bolt_outlined.svg

@@ -0,0 +1,3 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path fill-rule="evenodd" clip-rule="evenodd" d="M9.29787 2.8462C9.41607 2.90046 9.51178 2.98975 9.5701 3.10016C9.62841 3.21057 9.64605 3.3359 9.62028 3.45666L8.96749 6.51117H12.2195C12.334 6.51115 12.446 6.54191 12.5423 6.59976C12.6386 6.65762 12.7151 6.74013 12.7627 6.83748C12.8102 6.93482 12.8269 7.04291 12.8106 7.14885C12.7943 7.2548 12.7458 7.35413 12.6709 7.43504L7.49631 13.0184C7.40998 13.1115 7.29318 13.1752 7.16411 13.1997C7.03504 13.2241 6.90092 13.2081 6.78264 13.1539C6.66437 13.0997 6.56859 13.0104 6.5102 12.9C6.4518 12.7896 6.43408 12.6643 6.45979 12.5435L7.11259 9.48899H3.86054C3.74609 9.489 3.63405 9.45825 3.53776 9.40039C3.44147 9.34254 3.36498 9.26003 3.31742 9.16268C3.26986 9.06534 3.25322 8.95725 3.26949 8.85131C3.28576 8.74536 3.33423 8.64603 3.40916 8.56513L8.58377 2.98169C8.67012 2.88856 8.78699 2.82478 8.91616 2.80028C9.04533 2.77576 9.17953 2.79192 9.29787 2.8462Z" fill="black" fill-opacity="0.15" stroke="black" stroke-width="1.5"/>
+</svg>