fdo#74345: Some shared formulas cannot be exported as shared formulas.

Excel's shared formula has some restrictions that Calc's doesn't have.
So we need to check each shared formula token to see if we can export
it as shared when saving to Excel.  Refer to the "SharedParsedFormula"
section of the [MS-XLS] spec.

Change-Id: I0ffce26700d2773bbd2893743edc6c03682c2ed7
(cherry picked from commit 180f593fbfea238df97d006f6847bba3d9b0e317)
Reviewed-on: https://gerrit.libreoffice.org/8165
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>