stats: move out the total_connections from hot restart related stats

[botengyao]

#33907

total connections are not strictly related to hot_start

Commit Message: Additional Description: Risk Level: Testing: Docs Changes: Release Notes: Platform Specific Features: [Optional Runtime guard:] [Optional Fixes #Issue] [Optional Fixes commit #PR or SHA] [Optional Deprecated:] [Optional API Considerations:]

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Caused by: https://github.com/envoyproxy/envoy/pull/34432 was opened by botengyao.

see: more, trace.