[Bug]: fetch-depth: 0 fetches unnecessarily deep and wide causes slowdown in "Fetch report" step

### What happened?

Hi,

We're currently using your action within a few of our workflows and have noticed a slowdown as our mono repo gets larger (And has more history), with the "Fetch report from ${{ inputs.diff-storage }}" taking over 20s at some points.

I believe this is due to the "fetch-depth: 0" specified in the action.

https://github.com/insightsengineering/coverage-action/blob/50449af77a423ca017bf5496a6711db404d31811/action.yml#L131C9-L131C23

I'm not sure if this was an intentional thing, but it definitely appears to be unnessarily deep, as it fetches this from every branch as well.

From the actions-checkout page:

https://github.com/actions/checkout#usage

```yaml
# Number of commits to fetch. 0 indicates all history for all branches and tags.
# Default: 1
fetch-depth: ''
```

### Relevant log output

_No response_

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