Polarized SANS metadata: update instrument IDFs

[rbauststfc]

Part of #36147. See the design and requirements documents that are linked on that issue for more context.

The SANS IDFs should be updated to include the polarizing components that they would like to save metadata about. As per the design document, we have agreed that this should be done as follows:

For polarizers

  <component type="polarizer" name=”supermirror-polarizer”>
      <location y="0.0" x="1.0" z="0.0"/>
      <parameter name="device-name" type="string"> <value val="Supermirror polarizer" /> </parameter>
      <parameter name="device-type" type="string"> <value val="supermirror" /> </parameter>
  </component>
  <type name="polarizer" />

For analysers:

  <component type="analyzer" name=”helium-analyzer”>
      <location y="0.0" x="1.0" z="0.0"/>
      <parameter name="device-name" type="string"> <value val="3He Analyser" /> </parameter>
      <parameter name="device-type" type="string"> <value val="3He" /> </parameter>
     <parameter name="cell-length"> <value val="0.005” /> </parameter>
  </component>
  <type name="analyzer" />

For flippers (includes anything like spin-rotators that will also be recorded as a flipper in the NXcanSAS file):

  <component type="flipper" name=”polarizing-flipper”>
      <location y="0.0" x="1.0" z="0.0"/>
      <parameter name="device-name" type="string"> <value val="Polarizing flipper" /> </parameter>
      <parameter name="device-type" type="string"> <value val="coil" /> </parameter>
  </component>
  <type name="flipper" />

In each case, the device-name parameter is optional. If used it will be the name used for the component in the NXcanSAS file. If omitted, the component name will be used instead.

Depending on what is useful for our scientists, further information could be added, and the components could be given appropriate shapes, etc. However, the parameters shown above are the things that must be included in the definition (the location must also be included, but I believe that is already mandatory as part of defining any component).