We use `totalMetrics` with a `startTimeInNanos` and a call to `postIngest` to track the 'total time' that ingest is running for a given document. You can imagine it's a little stopwatch that we start and stop. Unfortunately, I think we're stopping the stopwatch just a little too soon, on the start side, we include the time spent transforming the document into an `IngestDocument`, but we do not include the (non-negligible) time transforming from an `IngestDocument` after the pipeline logic has run.

That is, the call to `sourceAsMap` is included:

https://github.com/elastic/elasticsearch/blob/d03664f84f15dcfcb900cf2d43121ca9d89bdda8/server/src/main/java/org/elasticsearch/ingest/IngestService.java#L905

But the call to `source` is not:

https://github.com/elastic/elasticsearch/blob/d03664f84f15dcfcb900cf2d43121ca9d89bdda8/server/src/main/java/org/elasticsearch/ingest/IngestService.java#L948

The consequence of this is that the `total` ingest stats doesn't actually reflect the true time spent in ingest code:

```
GET _nodes/stats?filter_path=nodes.*.ingest
{
  "nodes" : {
    "Aysm6ztIRne2ES5ktyuqtw" : {
      "ingest" : {
        "total" : {
          "count" : 1,
          "time_in_millis" : 110, <--- this should be a little higher than it is
```
server/src/main/java/org/elasticsearch/ingest/IngestService.java
throw new IllegalArgumentException(
                        String.format(
                            Locale.ROOT,
                            "version conflict, required version [%s] for pipeline [%s] but current version is [%s]",
                            request.getVersion(),
                            request.getId(),
                            currentVersion
                        )
                    );
                }
                var pipelineConfig = XContentHelper.convertToMap(request.getSource(), false, request.getXContentType()).v2();
                final Integer specifiedVersion = (Integer) pipelineConfig.get("version");
                if (pipelineConfig.containsKey("version") && Objects.equals(specifiedVersion, currentVersion)) {
                    throw new IllegalArgumentException(
                        String.format(
                            Locale.ROOT,
                            "cannot update pipeline [%s] with the same version [%s]",
                            request.getId(),
                            request.getVersion()
                        )
                    );
                }
                
                if (specifiedVersion == null) {
                    pipelineConfig.put("version", request.getVersion() == null ? 1 : request.getVersion() + 1);
                    try {
                        var builder = XContentBuilder.builder(request.getXContentType().xContent()).map(pipelineConfig);
                        pipelineSource = BytesReference.bytes(builder);
                    } catch (IOException e) {
                        throw new IllegalStateException(e);