## Description
A common use of `on_new_config` is to construct the `cmd` for starting
language servers based on the configuration. These language servers
require that the settings are finalized before it is run. It looks like
previous commits did use `add_hook_before` for the `lspconfig`
integration but it got moved to being `add_hook_after` when centralizing
it with the `lua_ls` and `jsonls` plugin integrations. We should revert
this back to `add_hook_before` so that the existing `on_new_config`
functions continue working.
## Description
After updating lspconfig, there is an error when I tried to open
`neoconf.json`.
The reason is that `lspconfig.util.available_servers` has been renamed
to `lspconfig.util._available_servers`.
([link](e118ce58da))
I fixed the issue and also update the deprecated code which is also come
from lspconfig.util
([details](0e234f4cad/lua/lspconfig/util.lua (L359-L362)))
<details>
<summary>error detail</summary>
```
Error 22:01:18 notify.error settings.nvim Failed to run client.before_init for settings/plugins/jsonls
....local/share/nvim/lazy/neoconf.nvim/lua/neoconf/util.lua:36: attempt to call field 'available_servers' (a nil value)
stack traceback:
...nvim/lazy/neoconf.nvim/lua/neoconf/plugins/lspconfig.lua:14: in function <...nvim/lazy/neoconf.nvim/lua/neoconf/plugins/lspconfig.lua:8>
...hare/nvim/lazy/neoconf.nvim/lua/neoconf/plugins/init.lua:14: in function 'fire'
...hare/nvim/lazy/neoconf.nvim/lua/neoconf/plugins/init.lua:20: in function 'fire'
...ocal/share/nvim/lazy/neoconf.nvim/lua/neoconf/schema.lua:45: in function 'get'
...re/nvim/lazy/neoconf.nvim/lua/neoconf/plugins/jsonls.lua:22: in function 'on_config'
....local/share/nvim/lazy/neoconf.nvim/lua/neoconf/util.lua:49: in function <....local/share/nvim/lazy/neoconf.nvim/lua/neoconf/util.lua:48>
[C]: in function 'func'
...al/share/nvim/lazy/nvim-lspconfig/lua/lspconfig/util.lua:53: in function <...al/share/nvim/lazy/nvim-lspconfig/lua/lspconfig/util.lua:51>
[C]: in function 'pcall'
...share/nvim/lazy/nvim-lspconfig/lua/lspconfig/configs.lua:217: in function 'make_config'
...share/nvim/lazy/nvim-lspconfig/lua/lspconfig/manager.lua:160: in function 'add'
...share/nvim/lazy/nvim-lspconfig/lua/lspconfig/manager.lua:220: in function <...share/nvim/lazy/nvim-lspconfig/lua/lspconfig/manager.lua:207>
[C]: in function 'pcall'
...l/share/nvim/lazy/nvim-lspconfig/lua/lspconfig/async.lua:5: in function <...l/share/nvim/lazy/nvim-lspconfig/lua/lspconfig/async.lua:4>
```
</details>
## Related Issue(s)
## Screenshots
according to
e118ce58da
## Description
<!-- Describe the big picture of your changes to communicate to the
maintainers
why we should accept this pull request. -->
fixed _available_servers is nil bug.
## Related Issue(s)
https://github.com/folke/neoconf.nvim/issues/104
<!--
If this PR fixes any issues, please link to the issue here.
- Fixes #<issue_number>
-->
## Screenshots
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github-actions[bot]
folke
Micah Halter
Chaz
github-actions[bot]
Zhou Fang
Vincent Law
leoatchina