feat: replace mock skywalking server with real one in CI

### Description

file `t/plugin/skywalking-logger.t`

```lua
add_block_preprocessor(sub {
my ($block) = @_;

my $http_config = $block->http_config // <<_EOC_;

server {
listen 1986;
server_tokens off;

location /v3/logs {
content_by_lua_block {
local core = require("apisix.core")

core.log.warn(core.json.encode(core.request.get_body(), true))
}
}
}
_EOC_
```