Use badge to indicate stderror rather than red text

[tlmii]

Since stderr isn't always used for logs that are considered errors (see prometheus logs, which are 100% stderr, as an example), coloring those logs red doesn't feel right. That said, we still want some indication that they came from stderr as opposed to stdout.

This PR adds a badge at the front of the log entry to indicate it comes from stderr. The badge is not selectable (so if the user highlights the logs to copy/paste, they won't get the "stderr" text as part of that).

[tlmii]

Example:

Some discussion about whether the badge should be red to still sort of indicate error... but we're starting with the accent color first and we'll see what feedback we get.

[karolz-ms]

Looks fantastic!