ADAP-1254: Add row access policy and table_tag config for snowflake

[b-per]

resolves #697

If approved, I am happy to add docs for it as well.

Problem

Today, it is not possible to set table tags or row access policies as part of CTAS statements. We can do it with post-hooks but there is a delay between the moment the object is created and the moment the tag or policy gets assigned, making potentially the object not available for some time.

Having those parameters as config allows making it part of the transaction.

Solution

Add 2 new parameters for Snowflake tables/views/incremental models:

• row_access_policy
• table_tag

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[b-per]

I will add support for Snowflake DT as well

[b-per]

I am not sure why mypy fails in the pre-commit

Run pre-commit run --show-diff-on-failure --color=always --all-files
check yaml...............................................................Passed
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
check for case conflicts.................................................Passed
Check for dbt-core usage in an adapter...................................Passed
black....................................................................Passed
flake8...................................................................Passed
mypy.....................................................................Failed
- hook id: mypy
- exit code: 1

dbt-snowflake/src/dbt/adapters/snowflake/relation_configs/dynamic_table.py:[105](https://github.com/dbt-labs/dbt-adapters/actions/runs/13946816131/job/39035875312?pr=901#step:4:110): error:
Item "None" of "Optional[MaterializationConfig]" has no attribute "extra" 
[union-attr]
                "row_access_policy": relation_config.config.extra.get("row...
                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
dbt-snowflake/src/dbt/adapters/snowflake/relation_configs/dynamic_table.py:[106](https://github.com/dbt-labs/dbt-adapters/actions/runs/13946816131/job/39035875312?pr=901#step:4:111): error:
Item "None" of "Optional[MaterializationConfig]" has no attribute "extra" 
[union-attr]
                "table_tag": relation_config.config.extra.get("table_tag")...
                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Found 2 errors in 1 file (checked 303 source files)

I ran the pre-commit hook locally and there was no error.

Even a pre-commit run --files src/dbt/adapters/snowflake/relation_configs/dynamic_table.py is all green for me locally.