help request: how set ingress apisix support proxy_protocol

### Description

Using an openstack loadbalancer attempting to capture client_ip. I am unsuccessful enabling the proxy_protocol section in the values file. Cannot find a key in the default values to get this accomplished.

I found previous help requests on the same topic but the solution was for 3.7 version of apisix the keys listed in that version's value file no longer exists. I have attempted the following as an override but the the config_map still have the proxy_protocol commented out.
```
apisix:
fullCustomConfig:
enabled: true
config:
apisix:
node_listen:
- 9080
enable_heartbeat: true
enable_admin: true
enable_admin_cors: true
enable_debug: false
enable_control: true
control:
ip: 127.0.0.1
port: 9090
enable_dev_mode: false
enable_reuseport: true
enable_ipv6: true
enable_http2: true
enable_server_tokens: true

# PROXY PROTOCOL ENABLED - This is the key section
proxy_protocol:
listen_http_port: 9181
listen_https_port: 9182
enable_tcp_pp: true
enable_tcp_pp_to_upstream: false
```
### Environment

- APISIX version (run `apisix version`):
NAME CHART VERSION APP VERSION DESCRIPTION
apisix/apisix 2.12.4 3.14.1 A Helm chart for Apache APISIX v3
- Operating system (run `uname -a`):
openshift 4.17 cluster
- OpenResty / Nginx version (run `openresty -V` or `nginx -V`):
- etcd version, if relevant (run `curl http://127.0.0.1:9090/v1/server_info`):
- APISIX Dashboard version, if relevant:
- Plugin runner version, for issues related to plugin runners:
- LuaRocks version, for installation issues (run `luarocks --version`):

Start with the APISIX Helm chart 2.12.4 values file and the generated ConfigMap, then compare how the fullCustomConfig override is rendered for the proxy_protocol section. Confirm which configuration key is supported in APISIX 3.14.1 and verify that the rendered ConfigMap enables client IP capture through the OpenStack load balancer.

Written by the indexing model from the issue text.