…chart (#11458)

**What this PR does / why we need it**:
Currently the Loki helm chart does not support defining s3 backoff
config settings. This PR adds support to the loki.commonStorageConfig
helper to add backoff config options when they're specified in the helm
values
**Which issue(s) this PR fixes**:
Fixes #<issue number>

**Special notes for your reviewer**:

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [ ] Documentation added
- [ ] Tests updated
- [ ] `CHANGELOG.md` updated
- [ ] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/setup/upgrade/_index.md`
- [x] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
PR](https://github.com/grafana/loki/commit/d10549e3ece02120974929894ee333d07755d213)
- [ ] If the change is deprecating or removing a configuration option,
update the `deprecated-config.yaml` and `deleted-config.yaml` files
respectively in the `tools/deprecated-config-checker` directory.
[Example
PR](https://github.com/grafana/loki/pull/10840/commits/0d4416a4b03739583349934b96f272fb4f685d15)

---------

Co-authored-by: Michel Hollands <42814411+MichelHollands@users.noreply.github.com>