feat: improve type.hashTreeRoot() using batch

[twoeths]

Motivation

• improve type.hashTreeRoot() using batch

Description

• instead of getRoots() and compute root from there, this PR implement getChunkBytes()
  • this compute root using merkleizeInto() which use batch there
  • reuse chunkBytesBuffer memory in type, almost no Uint8Array allocations in the middle
• new hashTreeRootInto() api. This is needed in case consumers want to reuse memory allocation there
• use allocUnsafe() of as-sha256 where it makes sense

cherry picked from #378