Improve log line decoding for kubernetes

What does this MR do?

Improve the way log line is decoded in kubernetes for the handling of the trapped command exit status.

More context on the change can be found here 👉🏿 !2824 (comment 564167886)

Why was this MR needed?

config.toml

concurrent = 1

[[runners]]
  name = "kubernetes"
  url = "https://gitlab.com/"
  token = "_REDACTED_"
  executor = "kubernetes"
  builds_dir = "/builds"
  [runners.kubernetes]
    image = "alpine:3.11"

What's the best way to test this MR?

Successfull job

gitlab-ci.yml

variables:
  DURATION: 10

job:
  script:
  - 'for i in $(seq 1 $DURATION); do echo $(date); sleep 1; done'
  - echo "done"

The job succeeds

Job Failure

gitlab-ci.yml

job:
  script:
  - ll

The job fails

What are the relevant issue numbers?

close : #27843 (closed)