[docdb] master UI make hash_split more readable

[jaki]

The master UI table page shows tablets and their partitions. If the table is default hash partitioned to two tablets, the partitions show as hash_split: [<start>, 32767) and hash_split: [32767, <end>). It's confusing at first glance, but 32767 maps to 0x7fff, which is the middle hash code between 0x0000 and 0xffff. It would be more understandable if we used hex notation or the dockey string representation that is used for range partitioned tables (e.g. range: [(<start>, DocKey([], [3])))). Do one of those changes to make this more readable.

[adzimzf]

Hi,
I interest to work on this, but since this is my first time, maybe it'll bit longer

[bmatican]

@adzimzf that would be perfectly fine! One suggestion, especially as this would be your first time contribution, might be useful to join our slack (http://yugabyte-db.slack.com/), as we could provide some more real time assistance in our #contributors channel.

[adzimzf]

Thank you @bmatican,
I'll try to read as much as I can first, if stuck I'll ask on the slack

[adzimzf]

Hi @bmatican I've created a PR for this issue,
please feel free to correct the PR, and sorry if there's a lot of mistakes 🙏

[jaki]

(From #6223) To clarify, this issue does not need to concern itself with YSQL tables which currently show no bounds for hash partitioning. I can create a separate issue for that if none exists.