cephfs-top: make cephfs-top display scrollable

[joscollin]

Fixes: https://tracker.ceph.com/issues/55197

• Implements Vertical and Horizontal scrolling of cephfs-top display. Use Up/Down Arrow Keys, PgUp/PgDn Keys or mouse for Vertical scrolling. Use Left/Right Arrow Keys and Home/End keys for Horizontal scrolling.
• Maintains the run_display and run_all_display applications separately for customising, if needed.
• Avoids the horizontal length (hlen) calculations of screen width. From now onwards, add n number of columns/fields and just Increase the PAD_WIDTH appropriately. Don't calculate the horizontal length anymore.
• This code currently supports a PAD_HEIGHT of 10,000, which means I'm expecting nearly 10,000 clients only. We could make it configurable or calculate it either (later). The important thing to notice is that the PAD_HEIGHT and PAD_WIDTH are constant with in the run display application. It could be configured, but it's not meant for changing dynamically. It's not meant for resizing and recreating dynamically. Create the pad once and use it until the end of the application. Only a portion of the viewport (clipping box) is refreshed at a time.
• The cephfs-top new UI with scrolling displays best in a maximised terminal window. It works in a tiny sized terminal window too, but the user has to give enough window size for him to see it fully functioning.

To test this well, try great number of clients like:

$ for i in {1..175}; do sudo mkdir -p /mnt/cephfs$i/; done
$ for i in {1..100}; do sudo ./bin/ceph-fuse -m <ip>:<port>  /mnt/cephfs$i/; done
$ for i in {101..150}; do sudo ./bin/ceph-fuse --client_mds_namespace fs1 -m <ip>:<port>  /mnt/cephfs$i/; done
$ for i in {151..175}; do sudo ./bin/ceph-fuse --client_mds_namespace fs2 -m <ip>:<port>  /mnt/cephfs$i/; done

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Checklist

• Tracker (select at least one)
  • References tracker ticket
  • Very recent bug; references commit where it was introduced
  • New feature (ticket optional)
  • Doc update (no ticket needed)
  • Code cleanup (no ticket needed)
• Component impact
  • Affects Dashboard, opened tracker ticket
  • Affects Orchestrator, opened tracker ticket
  • No impact that needs to be tracked
• Documentation (select at least one)
  • Updates relevant documentation
  • No doc update is appropriate
• Tests (select at least one)
  • Includes unit test(s)
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  • Includes bug reproducer
  • No tests

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[joscollin]

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[joscollin]

Test passed:
http://pulpito.front.sepia.ceph.com/jcollin-2022-10-24_10:06:27-fs-wip-F55197-cephfs-top-scroll-distro-default-smithi/

[joscollin]

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[tchaikov]

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[joscollin]

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[joscollin]

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[vshankar]

Waiting for an ACK from @neesingh-rh for merge.

[joscollin]

Waiting for an ACK from @neesingh-rh for merge.

Now this delay blocks me from creating a new PR (rebased). @vshankar Can you approve instead?

[vshankar]

Waiting for an ACK from @neesingh-rh for merge.

Now this delay blocks me from creating a new PR (rebased). @vshankar Can you approve instead?

Well ok :)