Sanitizer CI

[kylegranger]

Create a new CI to build and test polkadot-light-client using each of the sanitizer flags.

• five flags to test: address, leak, memory, thread, undefined.
• run on gcc, not clang
• run this weekly, at 06:00 UTC, Sundays.
• enable workflow_dispatch trigger as well

[kylegranger]

I have a version of sanitizer CI done for polkadot-light-client

• runs a build, each with one of four flags: ASAN (address), LSAN (leak), TSAN (thread), and USAN (undefined)
• the MSAN flag is not used, as neither gcc nor clang support it.
• the builds are run using gcc (no clang)
• LSAN and USAN both build and test with no errors. We are using per-flag Conan data cache: with no cache the build took 32 min 8 sec. After cache was built, 13 min 11 sec.
• TSAN and ASAN both build fine, but fail in test #3 (test_hex)
• the build is scheduled to run weekly, every Tuesday at 14:00 UTC. In the future, we may choose to run it on the weekend, or early Monday morning

I will create the PR when it does its first scheduled CI run, today at 14:00 UTC

[kylegranger]

This has been merged into master. Will continue to monitor before closing this ticket.