feat(entrypoint): add inbound mTLS profiles for HTTPS (#220)

Introduce reusable `inbound_mtls_profiles` in root config and support
`entrypoint.inbound_mtls_profile` to require client certificates for all
HTTPS traffic on an entrypoint. Profiles can trust the system CA store,
custom PEM CA files, or both, and are compiled into TLS client-auth
pools during entrypoint initialization.

Also add route-scoped `inbound_mtls_profile` support for HTTP-based
routes when no global entrypoint profile is configured. Route-level mTLS
selection is driven by TLS SNI, preserves existing behavior for open and
unmatched hosts, and returns the intended 421 response when secure
requests omit SNI or when Host and SNI resolve to different routes.

Add validation for missing profile references and unsupported non-HTTP
route usage, update config and route documentation/examples, expand
inbound mTLS handshake and routing regression coverage, and bump
`goutils` for HTTPS listener test support.

internal/route/provider/all_fields.yaml

@@ -10,6 +10,7 @@ example: # matching `example.y.z`
   no_tls_verify: true
   disable_compression: false
   response_header_timeout: 30s
+  inbound_mtls_profile: corp # optional, only supported when no global entrypoint inbound_mtls_profile is configured; selected by TLS SNI and Host/SNI must resolve to the same route
   ssl_server_name: "" # empty uses target hostname, "off" disables SNI
   ssl_trusted_certificate: /etc/ssl/certs/ca-certificates.crt
   ssl_certificate: /etc/ssl/client.crt