Add support for request body to be larger than 2GB on 32-bit devices

[aryan-25]

Motivation:

• The properties that store the request body length and the cumulative number of bytes sent as part of a request are of type Int.
• On 32-bit devices, when sending requests larger than Int32.max, these properties overflow and cause a crash.
• To solve this problem, the properties should use the explicit Int64 type.

Modifications:

• Changed the type of the known field of the RequestBodyLength enum to Int64.
• Changed the type of expectedBodyLength and sentBodyBytes in HTTPRequestStateMachine to Int64? and Int64 respectively.
• Deprecated the public var length: Int? property of HTTPClient.Body and backed it with a new property: contentLength: Int64?
  • Added a new initializer and "overloaded" the stream function in HTTPClient.Body to work with the new contentLength property.
  • Note: The newly added stream function has different parameter names (length -> contentLength and stream -> bodyStream) to avoid ambiguity problems.
• Added a test case that streams a 3GB request -- verified this fails with the types of the properties set explicitly to Int32.

Result:

• 32-bit devices can send requests larger than 2GB without integer overflow issues.

[fabianfett]

@swift-server-bot test this please

[fabianfett]

This already looks very god! Great patch! @Lukasa can you please check the API changes?

[Lukasa]

@swift-server-bot add to allowlist

[fabianfett]

Great change!