feat(config): add generic config Get support

[agermel]

This PR implements a new feature for the config package to support generic value retrieval》

Generic Get Method (New Feature)
Currently, retrieving configuration values requires manual type conversion (e.g., c.Value("key").Int()). This PR adds a Get[T] helper function that leverages Go generics to directly return the desired typed value.

// Before
port, err := c.Value("server.port").Int()

// After
port, err := config.Get[int](c, "server.port")

[agermel]

#3720 Solving this issue

[agermel]

Optimized Get[T] for primitive types by create a fast path that bypasses the overhead of Scan (unmarshall) for primitive types (bool, int, int64, float64, string)

	switch any(t).(type) {
	case bool:
		b, err := v.Bool()
		return any(b).(T), err
	case int64:
		i, err := v.Int()
		return any(i).(T), err
	case int:
		i, err := v.Int()
		return any(int(i)).(T), err
	case float64:
		f, err := v.Float()
		return any(f).(T), err
	case string:
		s, err := v.String()
		return any(s).(T), err
	}

[kratos-ci-bot]

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