Venue availability should check for lesson week

[li-kai]

Is your feature request related to a problem? Please describe.

When I search for venues on odd weeks, venue availability should mark classrooms that only have lessons on even weeks as free.

Describe the solution you'd like

Class schedules are given to us as strings. Parsing this would be pretty messy if we want to accommodate all edge cases, but it is reasonable to just parse even/odd weeks, and implement the search logic in https://github.com/nusmodifications/nusmods/blob/254a4df20a66fd3b60db5d41e6cace0dd8965729/website/src/utils/venues.ts#L37-L58.

Describe alternatives you've considered

Build an entire lossy parser so we can handle all the cases \o/

Additional context

https://t.me/NUSMods/11222