### Motivation

Add command `trace` to query trace by trace ID and visualize the traces

### Modification

- Add command `trace` to query and visualize traces.

- Move `main.go` to `cmd`, as per the recommendation of GO CLI package structure.

- Move GraphQL query to individual `*.graphql` file, for more friendly development, with IDE plugin.

### Result

- Traces can be queried and visualized by `swctl trace <trace id>`

- GraphQL queries can be debugged in IDE, with some plugins