Feature request: Add groupings to HexDump

**Describe the solution you'd like**
In the hexdump output block, add a groupings option which groups the hex side in groupings of X.

**Additional context**
This is thought out at G33kW33k, and putting this here in case it gets forgotten, and for tracking.

Currently, (and by default with this new option) the groupings are of size 1:
```
00000000 54 68 69 73 20 69 73 20 61 6e 20 65 78 61 6d 70 |This is an examp|
00000010 6c 65 20 6f 66 20 67 72 6f 75 70 69 6e 67 73 |le of groupings|
```
With a grouping of say 4 the output would look like:
```
00000000 54686973 20697320 616e2065 78616d70 |This is an examp|
00000010 6c65206f 66206772 6f757069 6e6773 |le of groupings|
```

This makes it easier when decoding protocols, where most of the encoded details are of the same fixed length.

Start by locating the HexDump operation and its existing output-formatting tests. Implement the requested grouping option while preserving grouping size 1 as the default, then verify that grouped output matches the examples and remains correct for incomplete final groups.

Written by the indexing model from the issue text.