Ability to select multiple instrument sessions should be considered

For the majority of use cases, users will want to have one and only one session selected. A small subset of use cases (beamline scientists setting up UDC) will want to select multiple sessions for interaction with ULIMS.

Where this "multiple session selection" is available should be considered, as having it attached to the global instrument session selection is likely to be confusing to users.

Start by finding the global instrument session selection entry point and tracing the UDC and ULIMS interaction flow. No files or tests are named; done requires an agreed location and behavior for selecting multiple sessions without confusing the default single-session selection.

Written by the indexing model from the issue text.