Starting v2

[m-mizutani]

This PR is base of version 2 of goerr

Motivation of v2

The goerr package previously utilized the With method to attach contextual information to errors. However, over time, several issues have been identified with this approach:

• It is unclear whether the method performs a destructive change on the original object.
• Actually, it does perform destructive changes, resulting in an error object that is not immutable.
• The implementation of a tagging feature led to the creation of a separate method, WithTags, which lacks consistency with the With method. This inconsistency may lead to similar issues when adding new features in the future.

To address these concerns, the goal of this pull request (PR) is to implement the functionality for attaching parameters to errors using the functional options pattern. This approach will make it more explicit that the generated error objects are immutable.

This change breaks backward compatibility, then I decided to start it as version 2.