fix: reduce chunked storage ChunkSize to fit within Kubernetes Secret limit (#2702)

OCPBUGS-85508

The chunked Helm release storage driver set ChunkSize to exactly 1MB
(1,048,576 bytes), which is the Kubernetes Secret data limit. The index
Secret stores both the first chunk and a JSON list of extra chunk names
(extraChunks), so any release requiring chunking exceeded the limit:

  Secret "sh.helm.release.v1.odf-operator.v1" is invalid:
    data: Too long: may not be more than 1048576 bytes

Reduce ChunkSize to (1024-8)*1024 (1,040,384 bytes), leaving 8KB of
headroom for the extraChunks field, and increase MaxReadChunks and
MaxWriteChunks from 10 to 11 to maintain total capacity above the
previous theoretical maximum.