[Swift Export] KT-63516

Add a sir-compiler-bridge module that adds Kotlin and C bridges
for SIR. As SIR is still WIP, the module accepts `BridgeRequest`
instances instead of SIR elements.

native/swift/sir-compiler-bridge/README.md

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+# Swift IR to Kotlin compiler bridges
+
+This module is responsible for the generation of "glue" code between Swift Export and Kotlin compiler.
+
+Swift does not "know" how to call Kotlin directly. But it has a C/C++/Objective-C interop, and we can leverage it for Swift Export.
+
+We do the following:
+1. Generate a Kotlin wrapper around the original Kotlin function with a primitive C-like ABI.
+2. Generate a C header with C declarations of these wrappers.
+3. Call these C functions from Swift functions.
+
+That's it! This approach also has the following advantages:
+1. All nuances of Kotlin compiler and Kotlin/Native runtime are hidden behind wrappers with a simple ABI. 
+So Swift Export (mostly) does not need to care about how Kotlin/Native works under the hood.
+2. The contract between Swift Export and Kotlin compiler is well-defined in the form of a set of compiler intrinsics.
+
+For the sake of simplicity, Kotlin wrappers are generated as Kotlin sources, 
+but later we can switch to direct generation of Kotlin Backend IR.