LUCENE-9907: Remove packedInts#getReaderNoHeader dependency on TermsVectorFieldsFormat

[iverase]

Replaces the usages of PackedInts#getReaderNoHeader with DirecReader#getInstance.

[jpountz]

I don't feel great about how we're guessing the number of bytes it takes to store the data. In every other place where we use DirectWriter/DirectReader we treat it as an implementation detail and make sure to record how many bytes were required in the file format. Could you update this PR to make the DirectWriter write into a temporary ByteBuffersDataOutput first so that we can know how many bytes were needed, and write this number as a vInt to the file format? This will use a few more bytes per block than the current file format, but I don't think that it would matter in practice.

On the read-side, I'd like to find a way to avoid creating a new slice for every block. Maybe we should create an anonymous RandomAccessInput that wraps the IndexInput like the default implementation of IndexInput#randomAccessSlice does? (minus the cloning)

[iverase]

I have added the length needed to store the int array so we can retrieve it before reading it.

In the read side, I found that wrapping the IndexInput is tricky as you might be changing the current position of the index at any point. I took a different approach and I am reading the data into a byte[] which is equivalent to what we were doing before by reading it into a long[].

[jpountz]

Great!