* Refactor compression namespaces across the project, making way for a possible introduction of alternatives to zlib compression in the llvm toolchain. Changes are as follows: * Relocate the `llvm::zlib` namespace to `llvm::compression::zlib`. * Code that explicitly needs `zlib` compression (IE zlib elf debug sections) should use `llvm::compression::zlib`. * Code interfacing with compressed profile data should use `llvm::compression::profile`. * Code interfacing with compressed serialized data should use `llvm::compression::serialize`.

* Refactor compression namespaces across the project, making way for a possible introduction of alternatives to zlib compression. Changes are as follows: * Relocate the `llvm::zlib` namespace to `llvm::compression::zlib`. * Code that explicitly needs `zlib` compression (IE zlib elf debug sections) should use `llvm::compression::zlib`. * Code interfacing with compressed profile data should use `llvm::compression::profile`. * Code interfacing with compressed serialized data should use `llvm::compression::serialize`.

* Refactor compression namespaces across the project, making way for a possible introduction of alternatives to zlib compression in the llvm toolchain. Changes are as follows: * Relocate the `llvm::zlib` namespace to `llvm::compression::zlib`. * Code that explicitly needs `zlib` compression (IE zlib elf debug sections) should use `llvm::compression::zlib`. * Code interfacing with compressed profile data should use `llvm::compression::profile`. * Code interfacing with compressed serialized data should use `llvm::compression::serialize`.