docs: document Snowflake driver options

[zeroshade]

Summary

Completes the option documentation tracked by #125 in go/docs/snowflake.md.

1. result_queue_size + example (captures apache/arrow-adbc#2328)

• Documented the relationship between adbc.rpc.result_queue_size and
  adbc.snowflake.rpc.prefetch_concurrency (bidirectionally) and added a Python
  set_options example — the missing piece #2328 explicitly asked for.
• Defaults (100 and 5) were verified against go/connection.go
  (defaultStatementQueueSize = 100, defaultPrefetchConcurrency = 5); the
  "default 5 / 10 workers / queue size 200" figures in #2328 describe the older
  upstream Python driver, not this one, so no values changed.

2. Descriptions for the previously type-only options

Filled in descriptions for every option that was listed with only a type:

• Timeouts (login_timeout, request_timeout, jwt_expire_timeout,
  client_timeout) — now documented as Go time.ParseDuration duration strings
  with their precise meaning.
• Key-pair auth: jwt_private_key (file path), jwt_private_key_pkcs8_value
  (inline PEM), jwt_private_key_pkcs8_password (passphrase for encrypted keys).
• okta_url, keep_session_alive, disable_telemetry, ocsp_fail_open_mode,
  identity_provider (WIF; values AWS/AZURE/GCP/OIDC), config_file
  (client easy-logging config).
• uri.host / uri.port / uri.protocol — including correcting uri.port to
  int and documenting the OCSP fail-open, port (443), and protocol
  (https) defaults.

Semantics were verified against the option parsing in go/driver.go and
go/database.go and the gosnowflake v2 Config fields — not guessed.

Testing

Docs-only change to go/docs/snowflake.md (static MyST section); no code paths
affected.

Closes #125. Captures apache/arrow-adbc#2328.