Enpower `egctl` with more advanced abilities

## Current State

`egctl` is a command line tool for making operate/debug Envoy Gateway easier. But for now, it just provides some basic abilities:

+ egctl config envoyproxy: Retrieve proxy configuration. (envoyproxy configdump)
+ egctl version: Retreve versions of envoygateway and envoyproxy.
+ egctl experimental stats envoyproxy: Retrieves Envoy metrics in the specified pod
+ egctl experimental translate: Translate Configuration from an input type to an output type. (gateway-api to xds, gateway-api-status)

## Work in process

+ egctl experimental access-logs: Streaming access logs from Envoy Proxy.

## What`s more

### Out of box operations

+ egctl install
+ egctl uninstall
+ egctl upgrade
+ egctl manifest

### Managed Resources Status

+ egctl status:
+ egctl status gatewayclass
+ egctl status gateway
+ egctl status xRoute
+ egctl status xPolicy

### Abstract EnvoyProxy CRD operations

+ egctl proxy --gatewayclass=eg scale --replicas=3
+ egctl proxy --gateway-class=eg concurrency --number=4
+ egctl proxy --gateway-class=eg bootsrap merge --from-file=new-bootstrap.json
+ egctl proxy --gateway-class=eg bootsrap replace --from-file=new-bootstrap.json
+ egctl proxy --gateway-class=eg service --type=clusterIP --loadBalancerClass=xxx
+ ...

### Configuration Validating

+ egctl validate
+ egctl analyze

### Web Console Access
> This should be put after CP/DP Observability is mostly finished.

+ egctl dashboard