Close leaked resources and reap editor processes

[kojah]

The Prometheus remote-write exporter discards the response from http.Do, so every metrics push leaks the response body and its connection. This change closes the response body. It also closes the response body in fetchTemplates, the temporary config file handle in git-remote-encore, the gzip writer when writing the wasm release artifact fails, and the gzip reader in the runtime config parser.

Editor launches now call Wait in the background so detached processes are reaped instead of remaining as zombies on Unix for the daemon's lifetime.

Testing:

• go build ./cli/cmd/encore
• go build ./cli/cmd/git-remote-encore
• go test ./cli/cmd/encore/app ./cli/cmd/git-remote-encore ./pkg/editors ./pkg/releaser/steps/tsparserwasm
• From runtimes/go: go test ./appruntime/exported/config ./appruntime/infrasdk/metrics/prometheus

I found these issues through a static analysis tool I'm developing called gohawk. If you're interested, let me know and I can open a separate PR to add gohawk to your linter configuration :) You can view more comprehensive information about the project on the documentation website: https://gohawk.dev

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