Use rowSx instead of rowStyle to style selected cell based on row record

[zhujinxuan]

This PR intends to add rowSxinstead of rowStyle for styling the Datagrid rows for two reasons:

1. Sx is more common in mui instead of style to style.
2. rowStyle will apply to the whole row. If one wants to highlight specific cells in the datagrid body, for example highlight duplicate phone numbers, they have to write their own DatagridBody and DatagridBodyRow. Meanwhile, rowSx can fix the problem.

rowStyle has been kept in this PR for compatibility.

I have not yet updated the spec and docs according to `rowSx'. If you think this change is good, I will update docs and spec in the same PR.

[fzaninotto]

Thanks. As this is a new feature, it should be PR'ed against next rather than master, and your PR should include unit tests and documentation for the new feature.

[zhujinxuan]

Got it! I will submit a new PR against the next branch.

[mshd]

Hi @zhujinxuan have you submitted your PR. I'm trying to change the background color of individual cells based on the record. I think your PR will make this possible.

[zhujinxuan]

@mshd I haven't yet submitted the new PR to next branch. I will do it on this weekend.

[mshd]

Great, appreciate it! @zhujinxuan

[mshd]

Hey @zhujinxuan did you get to it. Should I help?

[zhujinxuan]

@mshd The new PR is just finished and waiting for review.