Run Number Selection Changes

Changes requested to IPTS/run number selections.

Run number and IPTS number can be both integer and string. This might only matter when user load from existing files, or copy/paste from existing configurations.
Related to above, when multiple run number is separated by comma and quoted, then that string is considered as one run in drtsans. Those run numbers will be summed in reduction to increase counts (I think this clause is wired as well)

" It is possible to specify a set of scattering runs for a single sample that are to be summed together into a single data set for reduction. To do so, use the following format, which uses a single pair of quotes to enclose the list: "runNumber":{"run1, run2"}"

The exact schema of run number in drtsans reads as follows:
```
"runNumberTypes": {
  "anyOf": [{"type": "string", "minLength": 1},
            {"type": "integer", "minimum": 1},
            {"type": "array", "minItems": 1, "items": {"type": ["integer", "string"]}}],
  "dataSource": "events",
  "preferredType": "runstr"
},
```
The run number value can be an int / string or list combined with int and string
So it might be better to allow users to edit the text box after they selected from the proposed list.
Same criteria applies to background run numbers, if background is specified.

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