Improve warning alert component design

[gtsiolis]

Problem to solve

🅰️ The first version of the warning alert component design was based on high saturated colors[1] and didn't adapt on dark theme colors (see screenshots below) as we did with labels in #4607.

Delete deletion modal on light theme ☀️	Delete deletion modal on dark theme 🌔

Labels on light theme ☀️	Labels on dark theme ☀️

🅱️ In the latest design specs using ther warning alert component, we've tried to improve the colors of the warning alert component, see example in #7295 (comment).

Proposed design for the warning alert component

Proposal

Since this is using the AlertBox component, we could update this once and improve the UX of this component across the product.

Next steps could include improving the rest of alerts by clearly defining the available types (info, warning, error, etc) and documenting when to use which.

[jldec]

Assigned to @jankeromnes per #7295 (comment)