DJ was supported by Funda¸c˜ao para a Ciˆencia e a Tecnologia, Portugal, through scholarship PD/BD/150354/2019, under POCH funds, co-financed by the European Social Fund and Portuguese National Funds from MCTES, and by the Centre for Mathematics of the University of Coimbra, Portugal (UIDB/00324/2020, funded by the Portuguese Government through FCT/MCTES). EP partially supported by the Centre for Mathematics of the University of Coimbra (UIDB/00324/2020, funded by the Portuguese Government through FCT/MCTES) and by FAPERJ (grants E26/200.002/2018 and E26/201.390/2021). JMU partially supported by the King Abdullah University of Science and Technology (KAUST), Saudi Arabia, by Funda¸c˜ao para a Ciˆencia e a Tecnologia, through project PTDC/MAT-PUR/28686/2017, and by the Centre for Mathematics of the University of Coimbra (UIDB/00324/2020, funded by the Portuguese Government through FCT/MCTES).