Simplify SpikeDetectConfig, remove SpikeDetectOptions

[emmazhou]

Note that this will merge conflict with #18 which is also currently in flight; whatever order they land in, we should end up with:

message SpikeDetectConfig {
  oneof config {
    Thresholder thresholder = 1;
    TemplateMatcher template_matcher = 2;
  }
  uint32 bin_size_ms = 5;
}

[antoniaelsen]

just ping me when you merge, I will update cpp and ts