Add chip_crypto=boringssl flag

Fixes #24.

`boringssl` is bundled as part of the repo and built and statically linked into the resulting library, so it should get updates with every Matter SDK release.

I think this solution is much preferrable to running EoL openssl.

I verified this builds on github actions for [x86](https://github.com/leonm1/chip-wheels/actions/runs/7952221255/job/21706593163) and [Mac](https://github.com/leonm1/chip-wheels/actions/runs/7952221255/job/21706593214) (I don't have an aarch64 runner to test on).

Author: leonm1

.github/workflows/build.yaml

@@ -124,6 +124,7 @@ jobs:
       - name: Setup Build, Run Build and Run Tests
         run: |
           scripts/build/gn_gen.sh --args=" \
+                                          chip_crypto=\"boringssl\"
                                           enable_rtti=true \
                                           enable_pylib=true \
                                           chip_config_memory_debug_checks=false \
@@ -221,6 +222,7 @@ jobs:
       - name: Setup Build, Run Build and Run Tests
         run: |
           scripts/build/gn_gen.sh --args=" \
+                                          chip_crypto=\"boringssl\"
                                           enable_rtti=true \
                                           enable_pylib=true \
                                           chip_config_memory_debug_checks=false \