Implement lints to match internal linting behavior

[another-rex]

• All exported structs or functions need to have a comment
• Each library need one and only one comment about what this package does
  Our internal linters only expect this comment for just one of the package's files (so it'll complain if it's there for multiple files with package comments)
• There needs to be a new line at the end of a file
• TODOs should be associated with a buganizer number or GitHub issue number (Custom regex lint?)
  E.g. any line with // TODO:
  Must also include b/12345
  Or #123 in the same line
• //nolint comments. The internal linter has been fixed to allow this.
• Use "any" instead of "interface{}"

[cuixq]

also using "any" instead of "interface{}"

[cuixq]

I just fixed the internal linter to allow nolint directives so we don't need to worry about it any more.