Renamed set_error to kms_set_error

[MonkeybreadSoftware]

set_error is an awful generic name for a global function.

Sadly this easily conflicts with other libraries if you statically link this into an application.

please have us rename set_error to kms_set_error to avoid link errors with libraries/applications that also have set_error as function.

[kevinAlbs]

Thank you for the contribution @MonkeybreadSoftware. The change LGTM. src/kms-message is vendored from libmongocrypt. I would rather make the change in libmongocrypt first, then sync the source in the C driver. The C driver tests check the copy of src/kms-message does not diverge from libmongocrypt. If you are OK making the change in libmongocrypt, please do. Otherwise, we can make that change.

[MonkeybreadSoftware]

Thanks.

I made a pull request over there:
mongodb/libmongocrypt#923

I appreciate if you apply this and for future mongo-c-driver versions, I don't need to patch this locally.