final step of the toml migration

[glaslos]

Summary

Finishes the XML → TOML template cutover tracked in #638 / #534. PR #637 already added dual-format loading and migrated TFTP; this PR migrates every remaining protocol and profile, then drops XML/XSD support.

• Protocol servers now take a dict from {protocol}.toml (same contract as TFTP).
• Every shipped profile uses template.toml plus per-protocol *.toml. Auxiliary files stay as files (http/htdocs, SSL fixtures, SNMP MIB dirs).
• Startup validates TOML with the schema package (conpot/protocols/schemas.py).
• XML loaders, XSDs, and the xmllint workflow are removed. Custom XML templates are no longer supported.

What migrated

Default profile: bacnet, enip, ftp, http, ipmi, modbus, s7comm, snmp (TFTP was already TOML).

Other profiles: guardian_ast, IEC104, ipmi, kamstrup_382, plc_modbus, proxy, snmp.

Proxy uses proxy.toml via collect_proxies() (not name_mapping).

Test plan

• uv run pytest
• uv run black --check conpot/
• CI on this PR (pytest, black)