Add feature to side-by-side for building sxs's from two dates

[gmierz]

Recently, we've found that it would be useful to pass two dates as the revisions instead of the direct revisions. This would make it much simpler to see what two disparate changesets look like when compared to each other. For instance:

./mach perftest-tools side-by-side -t ... --base-platform ... --base-revision 01-09-2022 --new-revision 14-03-2023

We would need to look through all the pushes on a given date to find which ones (if any) have the requested browsertime tests. Note that this should not be available for the try branch.