improvement(logger): use 'white' as primary color (#5465)

Before this commit, our primary log color was chalk.grey and people
generally agree that it's too vague.

This commit changes the primary log color we've been using since we
first released Garden to chalk.white for better accessibility and more
fun.

In general we can make this configurable. But I figured I'd just bite
the bullet.

See also discussion in: #5464

core/src/logger/styles.ts

@@ -12,7 +12,7 @@ import chalk from "chalk"
  * A map of all the colors we use to render text in the terminal.
  */
 const theme = {
-  primary: chalk.grey,
+  primary: chalk.white,
   secondary: chalk.grey,
   accent: chalk.white,
   highlight: chalk.cyan,