Fix hasTable() returning stale results when mixing API and execute()

[dereuromark]

Summary

• Fix hasTable() returning stale results when mixing API calls with raw SQL via execute()
• When a table is created via API (e.g. $this->table()->create()) and dropped via execute(), hasTable() would incorrectly return true due to an internal cache
• The cache is now only used in dry-run mode where it's needed to track what tables "would" exist

Problem

// In a migration
$this->table('foo')->addColumn('bar', 'string')->create();
$this->table('foo')->exists();  // true ✓

$this->execute('DROP TABLE foo');
$this->table('foo')->exists();  // true ✗ (should be false!)

The $createdTables cache was being checked first in hasTable(), returning true without querying the database.

Solution

Only use the cache in dry-run mode. In normal execution, always query the database for accurate results.

Note:
There was also a 2nd issue in code.
The issue was a latent bug in SqlserverAdapter - it was passing the full nschema.ntable to dialect->hasTable() instead of just ntable. The cache was hiding this bug before.