Migrate to Conan 2.x

[thejohnfreeman]

This is a draft branch for testing CI with Conan 2.x. Contributors should switch soon. Conan 1.x package recipes are now frozen. They will no longer receive updates. The project builds just fine with Conan 2.x, and we can even simplify the build instructions.

[thejohnfreeman]

Current state:

• macOS works.
• Linux: dependencies job works, but test job fails when trying to run conan --version in the check environment step.
• Windows: takes forever. have never waited for the outcome, but appears to work.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.9%. Comparing base (ea1fffe) to head (53b620a).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5219     +/-   ##
=========================================
- Coverage     77.9%   77.9%   -0.0%     
=========================================
  Files          783     783             
  Lines        66677   66677             
  Branches      8108    8108             
=========================================
- Hits         51921   51918      -3     
- Misses       14756   14759      +3     

see 3 files with indirect coverage changes

[thejohnfreeman]

I believe this latest state will work for all checks. macOS may fail with 1 flaky error, as it has been doing for weeks. Everything else should pass.

[thejohnfreeman]

Where I left off:

• Windows build has a runtime mismatch. Perhaps Conan 2.x requires a different way to configure MSVC runtime. Need to investigate.
• conan test to build the example project that depends on xrpl is failing because Conan 2.x does not support the --require-override option.