Add tests and updates for go bindings

[Stavrospanakakis]

Update Go version to ^1.23, the actions/setup-go to v5, actions/checkout to v4 and github.com/stretchr/testify to v1.9.0.

Add test cases for the following model struct methods:

• New
• Close
• NewContext
• IsMultilingual
• Languages

Add test cases for the following context struct methods:

• SetLanguage
• IsMultilingual
• Language
• Process