docs: fix license headers and file identifications

[skyzh]

The style for header of each file is not consistent across all files in the project. The copyright date isn't updated to 2022. We should figure out a template for all of our file headers and fix this.

This is the style mostly found in this project:

//===----------------------------------------------------------------------===//
//
//                         BusTub
//
// rid.h
//
// Identification: src/include/common/rid.h
//
// Copyright (c) 2015-2019, Carnegie Mellon University Database Group
//
//===----------------------------------------------------------------------===//

[lmwnshn]

I think there is a script somewhere that did this formatting.

[skyzh]

Unluckily, the only .sh file in this repo is build_support/packages.sh. Do you mean some tools outside of this repo?

[lmwnshn]

Sorry, I'm bad at checking github notifs.

I don't remember if we have a newer version than Peloton, which is basically just a dumb header regex anyway.

I'm inclined to not care about this and punt to the future now that the semester is underway.