ENH: read_excel improve usecols
#### Is your feature request related to a problem?
No

#### Describe the solution you'd like
Let's imagine a excel database with multiple sheets
We can do `pd.read_excel(db, sheet_name=[0, 1], usecols=[0, 1])` and we would read the first and second columns of the first and second sheets.

Imagine we need to read the first and second columns from the first sheet and the second and third columns from the second sheet. A solution could be to pass to `usecols` a list of list, for example: `pd.read_excel(db, sheet_name=[0, 1], usecols=[[0,1], [1,2]])`. Both integer and string should be used inside the inner-list

#### API breaking implications
No, well I guess

#### Describe alternatives you've considered
Multiple run of `read_excel`
