Feature Request: Introduce VTTablet flag to control zstdInMemoryDecompressorMaxSize

[notfelineit]

Feature Description

Sometimes the current limit at which Vitess switches from in-memory buffer to streaming is still too high to prevent mysql OOMs:

vitess/go/mysql/binlog_event_compression.go

Line 65 in f6067e0

zstdInMemoryDecompressorMaxSize = 128 << (10 * 2) // 128MiB

It would be nice to be able to conditionally set this based on other infrastructure resource settings, as a VTTablet flag.

Use Case(s)

1. Our VTTablet is on a smaller Kubernetes pod size
2. We set zstdInMemoryDecompressorMaxSize to stream at a lower threshold, since VTTablet resources are less