Avoid GCC ubsan contexpr bug and add asan CI

[stephenberry]

PR: Add ASan CI and Fix Memory Leaks

Summary

This PR adds AddressSanitizer CI testing and fixes several memory leaks detected by ASan.

Changes

New ASan CI Workflow

• Added .github/workflows/sanitizers.yml with GCC 15 and ASan enabled
• Runs on ubuntu-24.04 with detect_leaks=1 to catch memory leaks in CI

GCC+UBSan Constexpr Fix (Issue #2287)

• File: include/glaze/core/reflect.hpp
• Moved constexpr auto& HashInfo = hash_info<keys_t> inside the nested lambda
• Workaround for GCC Bug 71962 where UBSan breaks constexpr evaluation of references captured from outer scope

Memory Leak Fixes

glaze_asio.hpp

• Added missing delete ptr in custom deleter for thread pool shared_ptr

http_server.hpp (streaming_utils namespace)

• Fixed circular reference in send_periodic_data() - self-capturing lambda kept streaming connections alive indefinitely
• Fixed circular reference in stream_collection() - same issue
• Both now use enable_shared_from_this pattern to properly break the reference cycle
• stream_collection() now copies the container to prevent dangling iterator issues

http_client_test.cpp

• Fixed circular reference in /slow-stream test handler using enable_shared_from_this pattern

Testing

All networking tests pass with ASan enabled:

• http_client_test: 22 passed
• http_server_api_tests: 49 passed
• http_server_post_test: 3 passed

[packit-as-a-service]

One of the tests failed for c7a825d. @admin check logs https://download.copr.fedorainfracloud.org/results/packit/stephenberry-glaze-2288/fedora-rawhide-ppc64le/10083041-glaze/builder-live.log, packit dashboard https://dashboard.packit.dev/jobs/copr/3207682 and external service dashboard https://copr.fedorainfracloud.org/coprs/build/10083041/

[packit-as-a-service]

One of the tests failed for 46ba491. @admin check logs None, packit dashboard https://dashboard.packit.dev/jobs/copr/3207777 and external service dashboard https://copr.fedorainfracloud.org/coprs/build/10083150/