Make overrides configmap block name consistent

[kavirajk]

What this PR does:
It edit tempo microservices jsonnet and makes the overrides_config block name consistent with Loki and Cortex

1. Loki - https://github.com/grafana/loki/blob/main/production/ksonnet/loki/overrides.libsonnet#L21
2. Cortex - https://github.com/grafana/cortex-jsonnet/blob/main/cortex/config.libsonnet#L469

Which issue(s) this PR fixes:
Fixes #NA

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[annanay25]

Is the name going to be used in a script/automation setting? Tempo has a consistent naming convention in the jsonnets at the moment, all configmaps have the _configmap suffix. Would be nice if we could retain that, but its ok to make the change if needed

[kavirajk]

@annanay25 Yea unfortunately I think we have to keep it _config. It's just that entitlement system expects this block name inside the jsonnet. Also NOTE: the name of final configmap on the k8 will still be tempo-overrides (no problem with that).

But I totally understand and agree with your naming consistency concern within tempo. I can happily change it to _configmap everywhere(including LOki and Cortex) once the migration is complete. :)