Previously the CI processor spent a surprising amount of time
validating the `expire_in` field for each build in the pipeline. It
turns out `ChronicDuration.parse` can be expensive because it uses
regular expressions and ActiveSupport numeric conversions.

We observe that builds often use a small set of `expire_in` values, so
we can cache the result of a previous validation.

For a pipeline like `gitlab-org/gitlab` that has 200 builds with 8
different `expire_in` values, we see a 28x improvement:

```
Calculating -------------------------------------
                 old     1.000  i/100ms
                 new    14.000  i/100ms
-------------------------------------------------
                 old      5.275  (± 0.0%) i/s -     27.000
                 new    149.409  (± 5.4%) i/s -    756.000

Comparison:
                 new:      149.4 i/s
                 old:        5.3 i/s - 28.32x slower
```

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/322386

Changelog: performance