[REQ] [Elixir] Use built-in JSON encoder and decoder

[efcasado]

Description

Elixir 1.18 added native built-in support for JSON encoding and decoding.

Tesla's JSON middleware supports the build-in module too.

Using the built-in JSON module would spare us the need to pull additional libraries like Jason. Also, the JSON module seems to implement a wider spectrum of the JSON specification. For example, Jason doesn't like atoms like :"TLS 1.3 / AES_128_GCM" and automatically generated modules like

defmodule Cloudflare.Model.UrlscannerGetScanV2200ResponseStatsTlsStatsInnerProtocols do
  @moduledoc """
  
  """

  @derive Jason.Encoder
  defstruct [
    :"TLS 1.3 / AES_128_GCM"
  ]

  @type t :: %__MODULE__{
    :"TLS 1.3 / AES_128_GCM" => float()
  }

  def decode(value) do
    value
  end
end

wouldn't compile and would result in the following error

== Compilation error in file lib/model/urlscanner_get_scan_v2_200_response_stats_tls_stats_inner_protocols.ex ==
** (Jason.EncodeError) invalid byte 0x2F in literal key: "TLS 1.3 / AES_128_GCM"
    (jason 1.4.4) lib/codegen.ex:120: Jason.Codegen."-check_safe_key!/1-lc$^0/1-0-"/2
    (jason 1.4.4) lib/codegen.ex:118: Jason.Codegen.check_safe_key!/1
    (jason 1.4.4) lib/codegen.ex:113: Jason.Codegen.escape_key/3
    (jason 1.4.4) lib/codegen.ex:107: Jason.Codegen.encode_pair/2
    (elixir 1.18.3) lib/enum.ex:1714: Enum."-map/2-lists^map/1-1-"/2
    (jason 1.4.4) lib/codegen.ex:48: Jason.Codegen.build_kv_iodata/2
    (jason 1.4.4) expanding macro: Jason.Encoder.Any.__deriving__/3
    lib/model/urlscanner_get_scan_v2_200_response_stats_tls_stats_inner_protocols.ex:10: Cloudflare.Model.UrlscannerGetScanV2200ResponseStatsTlsStatsInnerProtocols (module)

The built-in JSON module handles these scenarios well.

In order to be able to use the built-in JSON module, we would need to bump the minimum required version of Elixir from 1.10 to 1.18.