Refactor main.go (#3119)

* Refactor: reduce the use of strings.TrimSpace

* Refactor: use string attr before toProto

* Refactor parseEntry

- add value/attribute checker(check missing space)
- allow multiple spaces
- sort attributes
- improve readablity

* Refactor exportPlainTextList

- remove unnecessary variable
- improve readablity

* Remove support for partial include

This reverts e640ac2

It is problematic and I will implement a new one

* Refactor: promote refMap

* Feat: add support for partial include

- refactor inclusion logic
- add basic deduplicate

* Refactor exporting plaintext list

* Feat: add support for affiliation

A domain rule is always added to the list corresponding to the filename
it resides in. Additionally, you can now add affiliations to a domain
rule, and the rule will be added to the list specified by the
affiliation. Each affiliation begins with `&` and followed by the name
of the affiliation.

This helps us to reduce the number of data files without compromising
functionality, and avoid writing a same rule in different files.

* Feat: add advanced deduplicate for subdomains

only for domain/full subdomains without attr

* Refactor: import and use slices

* Refactor: improve code

Author: MkQtS