fix: scd type 2 support table properties

[eakmanrq]

Slack context: https://tobiko-data.slack.com/archives/C044BRE5W4S/p1757327355130579

Prior to this PR, users could define a partition by on their SCD type 2 model and it wouldn't be implemented properly on follow-up inserts/appends that replace the table. This PR fixes that.

[eakmanrq]

An append in this context seems to just be an insert where is_first_insert is False so updated it to reflect that and remove duplicate code.

[Copilot]

Pull Request Overview

This PR fixes SCD Type 2 model support for table properties like partitioned_by by ensuring these properties are properly passed to the adapter during follow-up inserts and appends that replace the table.

• Consolidates insert and append methods to use the same implementation
• Adds table properties parameters to SCD Type 2 adapter calls in the insert method
• Updates tests to verify partition properties are preserved in SCD Type 2 operations

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
sqlmesh/core/snapshot/evaluator.py	Modified insert method to pass table properties to SCD adapters; simplified append method to delegate to insert
tests/core/test_snapshot_evaluator.py	Added test case with partitioned_by property and verification of adapter calls
tests/core/engine_adapter/test_bigquery.py	Added BigQuery-specific test to verify partition properties in SCD Type 2 operations

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