Missing `darks` and `flats` parameters in loader YAML template

[yousefmoazzam]

Connected to DiamondLightSource/httomo#349

The loader YAML template in httomo-backends is currently under version control rather than autogenerated (and any autogenerated versions will be autogenerated from the old loader in httomo, rather than from the new "block loader"), and the current state of the YAML template is missing the darks and flats parameters:

httomo-backends/httomo_backends/yaml_templates/httomo/httomo.data.hdf.loaders/standard_tomo.yaml

Lines 1 to 13 in 7f9d963

	- method: standard_tomo
	module_path: httomo.data.hdf.loaders
	parameters:
	name: REQUIRED
	data_path: REQUIRED
	dimension: REQUIRED
	preview: REQUIRED
	pad: REQUIRED
	image_key_path: null
	rotation_angles:
	data_path: /entry1/tomo_entry/data/rotation_angle
	ignore_darks: false
	ignore_flats: false

From httomo's side, this means that the YAML checker rejects any YAML pipeline file containing those parameters, such as the I12 test pipeline in httomo that specifies separate darks/flats: https://github.com/DiamondLightSource/httomo/blob/7842bae27c1777545279aa36e8c10d9c4eeb489f/tests/samples/pipeline_template_examples/DLS/03_i12_separate_darks_flats.yaml#L14-L19