[Python] Improve Pydantic interop

[dbrattli]

Why

Libraries like Pydantic expect constructor arguments to be named arguments. This PR fixes this issue.

[<Erase>]
type Field<'T> = 'T

module Field =
    [<Import("Field", "pydantic")>]
    [<Emit("$0(frozen=$1)")>]
    let Frozen (frozen: bool) : Field<'T> = nativeOnly

    [<Import("Field", "pydantic")>]
    [<Emit("$0(default=$1)")>]
    let Default(value: 'T) : Field<'T> = nativeOnly

[<Import("BaseModel", "pydantic")>]
type BaseModel () = class end

[<Py.ClassAttributes(style="attributes", init=false)>]
type PydanticUser(Name: string, Age: bigint, Email: string option, Enabled: bool) =
    inherit BaseModel()
    member val Name: string = Field.Frozen(true) with get, set
    member val Age: bigint = Age with get, set
    member val Email: string option = None with get, set
    member val Enabled: bool = Field.Default(false) with get, set

let user = PydanticUser(Name = "Test User", Age=23, Email=None, Enabled=true)

This will now translate to:

class PydanticUser(BaseModel):
    Age: int
    Email: str | None
    Enabled: bool = Field(default=False)
    Name: str = Field(frozen=True)

PydanticUser_reflection = _expr1

user: PydanticUser = PydanticUser(Name = "Test User", Age = 23, Email = None, Enabled = True)