Migrate to aws-sdk-go-v2

[fudanchii]

This PR contains breaking change so we likely want to bump the major version.

Changes:

• aws-sdk-go-v2 now removes builtin interface for APIs, internalize the interface at internal/sqsiface so we can keep the testability intact.
• aws-sdk-go-v2 now removes builtin types and use Go primitives directly, also downgraded int64 to int32 for most of the int type, this PR comply with this change.
• all public methods now accept context.Context. We keep the old -WithContext pattern for easier migration. Follow the new pattern and removed all -WithContext methods.

[nabeken]

@fudanchii Thank you for your work!

I've updated the base branch to prep-v4 so we can do more work without landing actual changes into master.

all public methods now accept context.Context. We keep the old -WithContext pattern for easier migration.

Yeah, but we can only have a chance to do breaking changes now so I would like to remove the old WithContext methods and requires context.Context in the exposed methods.

[fudanchii]

Yeah, but we can only have a chance to do breaking changes now so I would like to remove the old WithContext methods and requires context.Context in the exposed methods.

@nabeken Understood, I removed the -WithContext methods with the latest change 🙏

[nabeken]

@fudanchii Thank you for your support! I've incorporated the PR into #85 and merged it.