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++ compiler requirement

• At least C++17

❗BREAKING CHANGE

We split the LoaderOptions into two kinds:

1. LoaderOptions : global-level load options
2. MessagerOptions: messager-level load options

So when setting options, there are some differences compared to before.

Compatibility resolution

patch_paths

options->patch_paths["PatchMergeConf"] = {"./path/to/file.json"};
// can be resolved to
auto mopts = std::make_shared<tableau::MessagerOptions>();
mopts->patch_paths = {"./path/to/file.json"};
options->messager_options["PatchMergeConf"] = mopts;

paths

options->paths["ItemConf"] = "./path/to/file.json";
// can be resolved to
auto mopts = std::make_shared<tableau::MessagerOptions>();
mopts->path = "./path/to/file.json";
options->messager_options["ItemConf"] = mopts;