Allow configurable max_request_header_size

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#### Is your feature request related to a problem? Please describe.

We have a multi-tenancy backend where identities and roles are embedded inside the request header. Default Envoy's HTTPConnectionManager header size is 60KB but we need a lot more than that. However, after tinkering with escape-hatch configurations with custom listeners and cluster, we couldn't figure out what was needed to make it work.

#### Feature Description

Allow configurable `max_request_header_size` [(defined here)](https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto#:~:text=scheme%20handling%20applies.-,max_request_headers_kb,-(UInt32Value)%20The) as part of the ServiceDefault or ProxyDefault manifest

#### Use Case(s)

Systems that use a lot of headers

#### Contributions

After tinkering with Consul for a bit, i found that `command/connect/envoy/bootstrap_config.go` contains the template for such listener. Happy to contribute if I can get a confirmation that that's where I should be editting though.