reapi c++: add satisfy endpoint

[vsoch]

Problem: the c++ bindings do not have satisfy support. Solution: add satisfy to them.

In practice I was adding this for exposure to the Go bindings, but I do not think it is necessary, because the Go bindings use the C bindings, which already have reapi_cli_match_satisfy. I saw that match_allocate seems to have support to provide the SATISFIABILITY match_op, which is provided to the traverser, so I tried to call that same function. I am opening this PR in case it is interesting or useful. If not, please close and disregard.

If the PR is desired, here are questions I have:

• I notice the general pattern for functions is to return a return code (0 success, -1 failure) and then take references to variables provided by the user (that are updated). I assume since we don't know what those are coming in as, we should set them to what we want for a default (for example, -1 for satisfied "no").
• I'm not adding Go tests here because (at least I want) the main Go wrappers to be in fluxion-go. I am going to do some PRs there shortly to update the go version.
• That said, how are the bindings tested? I couldn't find the tests in here.
• The reapi_cli seems to support the overhead variable since it calls match_allocate under the hood, which (I think?) sets it. But the module (by way of the rpc) doesn't seem to have that, so the signatures are different. Is that an issue?
• As best as I could tell, the RPC only returns 0 when it is a satisfy "YES"
• It's not clear to me what the "at" variable would be given a satisfy match_op. Reading the docstring, it sounds like a "yes" is >= 0 so I used that, but I'd like to understand why. It's hard to read this code because the variable "at" is really tiny and a substring of other variables and my eyesight is bad in my elderly dinosaur years. :laughing:

And again, if this is not of interest, please disregard! Going to do some work on fluxion-go next.

[codecov[bot]]

Codecov Report

Merging #1184 (f08ad38) into master (1c68ec6) will decrease coverage by 0.2%. Report is 31 commits behind head on master. The diff coverage is 0.0%.

:exclamation: Current head f08ad38 differs from pull request most recent head c9fb2bf. Consider uploading reports for the commit c9fb2bf to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1184 +/- ## ======================================== - Coverage 73.9% 73.8% -0.2% ======================================== Files 103 102 -1 Lines 14396 14396 ======================================== - Hits 10644 10627 -17 - Misses 3752 3769 +17 ``` | [Files](https://app.codecov.io/gh/flux-framework/flux-sched/pull/1184?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework) | Coverage Δ | | |---|---|---| | [resource/reapi/bindings/c++/reapi\_cli\_impl.hpp](https://app.codecov.io/gh/flux-framework/flux-sched/pull/1184?src=pr&el=tree&filepath=resource%2Freapi%2Fbindings%2Fc%2B%2B%2Freapi_cli_impl.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework#diff-cmVzb3VyY2UvcmVhcGkvYmluZGluZ3MvYysrL3JlYXBpX2NsaV9pbXBsLmhwcA==) | `36.8% <0.0%> (-0.6%)` | :arrow_down: | | [resource/reapi/bindings/c++/reapi\_module\_impl.hpp](https://app.codecov.io/gh/flux-framework/flux-sched/pull/1184?src=pr&el=tree&filepath=resource%2Freapi%2Fbindings%2Fc%2B%2B%2Freapi_module_impl.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework#diff-cmVzb3VyY2UvcmVhcGkvYmluZGluZ3MvYysrL3JlYXBpX21vZHVsZV9pbXBsLmhwcA==) | `50.3% <0.0%> (-6.8%)` | :arrow_down: | ... and [6 files with indirect coverage changes](https://app.codecov.io/gh/flux-framework/flux-sched/pull/1184/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework)

[vsoch]

I am sorry codecov bot, please forgive my sins :pray: