The encoding.DecompressZSTD* consistently updates the vm_zstd_block_decompress_calls_total metric.
Also make the follwing improvements after the commit 10f7cd2ffc:
- Add encoding.DecompressZSTDLimited() function and use it instead of zstd.DecompressLimited,
so it properly updates vm_zstd_block_decompress_calls_total metric.
- Clarify description for the encoding.DecompressZSTD* and zstd.Decompress* functions.
Previously, zstd Decoder didn't take in account Request Size limits
applied by VictoriaMetrics components. And in case of incorrectly formed zstd block, VictoriaMetrics
component may allocate extra memory. Which may lead to the OOM errors.
This commit makes ingest endpoints check frame content size and window size headers based on MaxRequest Limits.
