[docdb] master UI hash_split of last partition should be inclusive

Jira Link: DB-4659 The master UI table page has tablets with their partition boundaries. Recent commit dca4cf4ef52d768ea955ffe9a1b0b7ceffd20a9c made the format of the boundaries into hex notation. It also converted the "start" and "end" words to 0x0000 and 0xffff, respectively.

Now, it's a lot more obvious that there's an issue with all the boundaries being [foo, bar), foo being inclusive and bar being exclusive. Before, it looked like [foo, <end>), which is sort of fine depending on your interpretation of "end"; now, it looks like [foo, 0xffff), which is definitely incorrect. Change that last partition to be all inclusive so that it looks like [foo, 0xffff]. As of now, this is only applicable to YCQL hash partitioned tables.