Add pragma statements automatically if sqlite

[jakekaplan]

closes: #8060

Automatically adds PRAGMA statements for sqlite migrations to the migration template. This is referenced in the docs to include for sqlite migrations. This removes the manual step so they're added automatically if connected to a sqlite db.

Example:

prefect server database revision -m test

# sqlite migration
...
def upgrade():
    op.execute("PRAGMA foreign_keys=OFF")
    # ### commands auto generated by Alembic - please adjust! ###
    pass
    # ### end Alembic commands ###
    op.execute("PRAGMA foreign_keys=ON")

def downgrade():
    op.execute("PRAGMA foreign_keys=OFF")
    # ### commands auto generated by Alembic - please adjust! ###
    pass
    # ### end Alembic commands ###
    op.execute("PRAGMA foreign_keys=ON")

# postgres migration
...
def upgrade():
    
    # ### commands auto generated by Alembic - please adjust! ###
    pass
    # ### end Alembic commands ###
    

def downgrade():
    
    # ### commands auto generated by Alembic - please adjust! ###
    pass
    # ### end Alembic commands ###

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