aws-c-io: fix interface definition for shared lib on windows + bump s2n + add package_type

[SpaceIm]

• add AWS_IO_USE_IMPORT_EXPORT interface definition. This definition is mandatory to properly define __delcspec(dllimport) if shared on windows.It's very important since aws-c-io has at least one global symbol in its interface. I've seen this issue while trying to build aws-c-http shared against aws-c-io shared with Visual Studio. It was failing with h1_connection.c.obj : error LNK2019: unresolved external symbol g_aws_channel_max_fragment_size referenced in function s_connection_new (g_aws_channel_max_fragment_size is a global symbol defined in aws-c-io, so it MUST have __declspec(dllimport) at consume time).
• add package_type
• bump s2n

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[SpaceIm]

waiting for #17100, #17105 & #17122

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All committers have signed the CLA.

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 7 (2825759ef029036898087cd33baecd7e0c98452e):

• aws-c-io/0.13.4@:
  All packages built successfully! (All logs)

• aws-c-io/0.11.2@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.20@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.9@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.5@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.13@:
  All packages built successfully! (All logs)

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Conan v2 pipeline ✔️

Note: Conan v2 builds may be required once they are on the v2 ready list

All green in build 5 (2825759ef029036898087cd33baecd7e0c98452e):

• aws-c-io/0.13.4@:
  All packages built successfully! (All logs)

• aws-c-io/0.11.2@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.13@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.20@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.9@:
  All packages built successfully! (All logs)

• aws-c-io/0.10.5@:
  All packages built successfully! (All logs)

[SpaceIm]

@uilianries @jwillikers @ericLemanissier @jcar87 @prince-chrismc could you review please? There are several other aws PRs to merge before aws-sdk-cpp PR can pass v2 pipeline, and this one is the current bottleneck of other aws PRs (then #17107 & #17110 will be the next bottlenecks, then #17108 & #17111, then #17117, then #17120, and finally we could build #17125 which has been opened 2 months ago 😐 ).