Wrong params for proxy_on_vm_start

[dev-null-undefined]

https://github.com/proxy-wasm/spec/blob/main/abi-versions/v0.2.1/README.md#proxy_on_vm_start

The proxy_wasm_spec specifies that the second argument for proxy_on_vm_start sould be the VM config size

Since from my knowladge of the code you do not support VM config yet, it would make sense to hard code 0 there with maybe a comment /* TODO VM configuration */

ngx_wasm_module/src/common/proxy_wasm/ngx_proxy_wasm.c

Line 1216 in 883b627

rexec->id, rexec->root_id);

[thibaultcha]

Feel free to send a PR for this one as well. We do support VM configuration via our module directive.