[SwiftBuild] BSP-based SourceKit-LSP integration

[owenv]

Description

Umbrella tracking BSP for SourceKit-LSP integration

#9129
swiftlang/swift-build#782
swiftlang/swift#85078

Expected behavior

No response

Actual behavior

No response

Steps to reproduce

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Swift Package Manager version/commit hash

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Swift & OS version (output of swift --version && uname -a)

No response