Move pre-specializations of popular types away from the stdlib

[swiftix]

Pre-specializations were only used by Onone builds, but were kept inside the standard library dylyb anyways. This commit moves all the pre-specializations into a dedicated Swift module and a dynamic library, which are only used by Onone builds.

This reduces the code size of libswiftCore.dylib by 4%-5%.

This PR fixes some problems discovered when trying to merge the PR #1392:

• There were some issues with debug builds
  • The new library was not using -parse-stdlib
  • CMake rules for Swift files were not making sure that they always depend on SwiftOnoneSupport
• Not all pre-specializations available when Prespecialized.swift was part of the stdlib were available in this new dedicated library for Onone.

[swiftix]

@swift-ci Please test

[gribozavr]

Don't we want to do this block unconditionally, even when building non-optimized libraries?

[swiftix]

@gribozavr If we do this whole block unconditionally, then we introduce a link dependency on swiftSwiftOnoneSupport even in Release builds, which results in this dylib being linked to the apps even though it is not used.

[swiftix]

@gribozavr But the two removal operations could be performed unconditionally, I agree. Because swiftSwiftOnoneSupport and stdlib do not depend on swiftSwiftOnoneSupport under any circumstances.

[swiftix]

@phausler @parkera I'm ready to merge on my side. But I still need your corresponding foundation changes to be committed, otherwise the Linux build will fail. Please see my email for details.

[phausler]

@swiftix can you provide a pull request with the appropriate changes to the build scripts?

[swiftix]

@phausler Will do.

[swiftix]

@phausler I provided a PR you asked for. You can review it at swiftlang/swift-corelibs-foundation#266

[swiftix]

@phausler Please let me know when you are ready to merge, so that we can do it in sync to avoid any broken builds.