Create DynamoRIO kernel module

We are working on reviving and improving [drk](https://github.com/DynamoRIO/drk/) to make it work with modern kernel and current DR. We have made some progress, and I think merging it into this repo would make it much easier to collaborate. My plan to make this process as smooth as possible is as following

1. Bootstrap the build system and CI pipeline with a boilerplate kernel module as placeholder.
2. Add core DR files as dependencies for the kernel module, so that we can first fix them to compile in a freestanding kernel environment. These include removing/replacing user space header (stddef.h, stdarg.h, etc.) and excluding logic that do not apply to the kernel from kernel build (e.g., floating point numeric, rseq).
3. Import actual kernel module code and tests from the drk repo.
4. Add aarch64 support.

Start by reviewing the existing drk repository and the proposed build-system and CI bootstrap. Then examine the core DynamoRIO files that must compile in a freestanding kernel environment, followed by the referenced kernel-module code and tests. The work is complete when the module builds and its tests run, with the planned aarch64 support included.

Written by the indexing model from the issue text.