This is a duplicate of PR#867 as the original branch is not able to get update.

Change Description:

Cell value types have been introduced to custom function input parameter type. We decided to move it to a new attribute "cellValueType" for backward compatibility, so that older client won't break on unknown types.
"cellValueType" works as follows:
When "type" is one of "boolean"/"number"/"string", "cellValueType" won't be parsed by Excel. When "type" is "any" and "cellValueType" is a valid cell value type, the cell value type will be used as custom function parameter type. If "cellValueType" is invalid, Excel will use the fallback "type" "any".

Sample function metadata before change:

{
    "description": "Test Excel.CellValue parameter",
    "id": "TESTCELLVALUEPARAM",
    "name": "TESTCELLVALUEPARAM",
    "parameters": [
        {
        "name": "x",
        "type": "cellvalue"
        }
    ],
    "result": {}
}

after change:

{
    "description": "Test Excel.CellValue parameter",
    "id": "TESTCELLVALUEPARAM",
    "name": "TESTCELLVALUEPARAM",
    "parameters": [
        {
        "name": "x",
        "type": "any"
        "cellValueType": "cellvalue"
        }
    ],
    "result": {}
}

1. Do these changes impact command syntax of any of the packages? (e.g., add/remove command, add/remove a command parameter, or update required parameters)
   No

2. Do these changes impact documentation? (e.g., a tutorial on https://learn.microsoft.com/office/dev/add-ins/overview/office-add-ins)
   Cell value types are not public yet.

3. Validation/testing performed:
   Updated and ran tests.