Fix/underscore account hostname

[Pazuzzu]

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue
   to your PR.

Fixes #1839
The async connector fails with SSL hostname mismatch on Python 3.11+ when the account name contains underscores (e.g. my_org_account), because the resulting hostname is rejected during TLS verification.

I saw that it's already being discussed in #1839. @sfc-gh-dszmolka's test confirmed that both _ and - resolve to the same account.
(I've seen that the official Snowflake docs also document this now in: https://docs.snowflake.com/en/user-guide/admin-account-identifier)

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am modifying authorization mechanisms
   • I am adding new credentials
   • I am modifying OCSP code
   • I am adding a new dependency

3. Please describe how your code solves the related issue.

This one-liner in construct_hostname() normalizes underscores to hyphens before building the FQDN, same approach dbt-snowflake shipped in dbt-labs/dbt-snowflake#1068.

Note: this reopens #2897, which was closed for administrative reasons unrelated to the code.