Improve performance of index settings validation #130804
Description
archiveUnknownOrInvalidSettings can be fairly slow and impact startup times if the number of index settings is high and settings are complex, e.g. analyzers. We've seen this take up to 25mins for ~3M index settings.
We should investigate the performance bottleneck and identify improvements.
One potential improvement could be to not validate the same settings over and over again if the same for various indices.
Also, we might be able to skip validation on non-master nodes entirely.