Add @encryption_list parameter for backup encryption testing

- Add @encryption_list parameter (0, 1, or 0,1 for both)
- Pre-compilation ALTER TABLE guard adds encryption column to existing
  backup_performance_results tables before ALTER PROCEDURE compiles,
  preventing Msg 207 invalid column name at compile time
- CREATE TABLE inside proc body updated to include encryption column
  on fresh installs, matching original pattern
- DMK and certificate pre-validation before test loop with descriptive
  RAISERROR messages using @msg variable pattern
- Certificate name resolved once before loop, not per iteration
- encryption threaded through cursor, FETCH, progress messages,
  BACKUP WITH clause (AES_256), and INSERT INTO results table
- encryption column added to all 5 result sets, GROUP BY, PARTITION BY
- Result set 2 now partitions on compression+encryption pairing
- Result set 3 adds encryption UNION ALL block for parameter impact
- Version bumped to 1.1, version_date 20260518
- Tested on SQL Server 2022 CU24, confirmed AES_256 encryption via
  msdb.dbo.backupset encryptor_type and thumbprint verification

Author: bfountain-1976