Upgrade compiler version && Support encode for type duration and datetime

[MaryGao]

fixes #1828

• Upgrade compiler to v0.44
• Support the @encode decorator and below are cases:

model SimpleModel {
      @encode("rfc3339")
      createdAt: utcDateTime;                   // TypeScript type: as usual
}

model SimpleModel {
      @encode("unixTimestamp", int32)
      createdAt: utcDateTime;                 // TypeScript type: number
}

model SimpleModel {
      @encode("seconds", float64)
      prop: duration;                         // TypeScript type: number
}

model SimpleModel {
      @encode("ISO8601")
      prop: duration;                       // TypeScript type: string
}

[MaryGao]

Issue is tracked here: #1842