chore: Move CosetIndex and CommitmentIndex into kzg_multi_open #240

Job	Run time
Build - x86_64-apple-darwin	1m 8s
Build - aarch64-apple-darwin	1m 15s
Build - x86_64-unknown-linux-gnu	1m 12s
Build - aarch64-unknown-linux-gnu	1m 26s
Build - x86_64-pc-windows-msvc	15m 42s
Build - aarch64-pc-windows-msvc	15m 47s
Test - x86_64-apple-darwin - node@20	59s
Test - aarch64-apple-darwin - node@20	28s
Test - x86_64-unknown-linux-gnu - node@20	31s
Test - aarch64-unknown-linux-gnu - node@20	5m 4s
Test - x86_64-pc-windows-msvc - node@20	1m 23s
Test - aarch64-pc-windows-msvc - node@20	19s
Publish	24s
	45m 38s

Provide feedback