Set GOMEMLIMIT for Gitaly container

What does this MR do?

Setting this env variable can help avoid OOM related errors induced by the Go garbage collector. Go is not aware of what the container's memory limits are, by setting this we can configure a soft memory limit. It will be more aggressive running gc cycles (increasing cpu usage) getting closer to the limit and try to use all the live heap before increasing more memory for the heap.

Related issues

Related issue: gitlab-org/gitaly#6067

Author checklist

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Expected (please provide an explanation if not completing)

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• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.