feat: parameterise the LogGroupName for lambda-promtail CloudFormation template

[InsomniaCoder]

What this PR does / why we need it:

while testing #12728 I realised that with the current template, the log group name is hardcoded. so, we cannot refer to this lambda-promtail.yaml from upstream directly but need to copy and make a modification.

paratemerise the log group name will allow us to use directly the upstream template for creating the subscription flow.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• 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
• 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

[InsomniaCoder]

closing to combine all changes in the main PR