cpp(BREAKING)!: support both global-level and messager-level load options

[wenchy]

Related PRs

• Go: load(options): support both global-level and messager-level options, and add new option LoadFunc

C++ standard requirement

• At least C++17

❗BREAKING CHANGE

We split the LoadOptions into two kinds:

1. LoadOptions: global-level options for Hub::Load.
2. MessagerOptions: messager-level options for Messager::Load.

So when setting Hub::Load options for messager-level options, there are some differences compared to before.

Compatibility resolution

paths

options->paths["XXXConf"] = "./path/to/XXXConf.jsonn";
// changed to
auto mopts = std::make_shared<tableau::MessagerOptions>();
mopts->path ="./path/to/XXXConf.jsonn";
options->messager_options["XXXConf"] = mopts;

patch_paths

options->patch_paths["PatchXXXConf"] = {"./path/to/PatchXXXConf.json"};
// changed to
auto mopts = std::make_shared<tableau::MessagerOptions>();
mopts->patch_paths = {"./path/to/PatchXXXConf.json"};
options->messager_options["PatchXXXConf"] = mopts;