Change data for people counting example and built-in direction

[shanyu-sys]

Why this change?

1. We used an internal video to test people counting, while it cannot be accessed by users. Find another public video data to count pedestrians. A new public video data can be downloaded here
2. Move the direction property into property lib
3. within_regions can accept a single region(a list of coordinates)

What does this PR include?

1. Tune REGION for the new dataset.
2. Enhance within_regions interface to accept a single region input. Internally, we will convert a single region to a list of regions. API doc for within_regions has also be added.
3. Move the direction property inside. Since it is complicated mainly for debugging, user may get confused if it is in the example.

User API changes

1. within_regions(regions), regions can be either one region or a list of regions
2. user can directly use direction property in their query

How did I test the PR?

With people counting example

New dependencies included

No

Related issue

https://github.com/VQPy/VQPy-internal/issues/21