sql: cleanup code from obsolete macros

Removes the following unused macros:
SQL_OMIT_AUTOINCREMENT
SQL_OMIT_CONFLICT_CLAUSE
SQL_OMIT_PRAGMA
SQL_PRINTF_PRECISION_LIMIT
SQL_OMIT_COMPOUND_SELECT
SQL_POWERSAFE_OVERWRITE
SQL_OMIT_PROGRESS_CALLBACK
SQL_OMIT_AUTORESET
SQL_OMIT_DECLTYPE
SQL_ENABLE_COLUMN_METADATA
SQL_TRACE_SIZE_LIMIT
SQL_OMIT_LIKE_OPTIMIZATION
SQL_OMIT_OR_OPTIMIZATION
SQL_OMIT_BETWEEN_OPTIMIZATION
SQL_EXPLAIN_ESTIMATED_ROWS
SQL_ENABLE_COLUMN_USED_MASK
SQL_DISABLE_DIRSYNC
SQL_DEBUG_SORTER_THREADS
SQL_DEFAULT_WORKER_THREADS
SQL_LIMIT_WORKER_THREADS
SQL_MAX_WORKER_THREADS
SQL_ENABLE_MEMORY_MANAGEMENT
SQL_ENABLE_UNKNOWN_SQL_FUNCTION
SQL_SUBSTR_COMPATIBILITY
SQL_ENABLE_STMT_SCANSTATUS
Removed the remains of multithreading in the VDBE
sorting tools.
Updates tests.

Closes #3978