### 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

### Motivation

Adopt the new API of multiple linear metrics, https://github.com/apache/skywalking/pull/4214

### Modification

- Rewrite the pxx metrics with the new API

- Slightly refactor the GraphQL client into individual package, according to the query protocol

- Enhance the Ascii Graph display style

### Result

- CLI is compatible with the latest backend

- Ascii Graph can display multiple charts in one screen

* [Feature] Add endpoint command, refactor Makefile to cross build target

* Add missing documentation and polish

* Fix bug

* Polish

* Re-organize documentations and collapse details for simplicity

* Add some common use cases

* Polish

* Add ascii graph

Set up the graphql client, schema and implement a service command
for reference

Modifications:

- Set up GraphQL client
- Implement service ls command

Result:

GraphQL client can be reused by other commands