Add osd parser

[jgrund]

Add a new parser for osd stats and remove from other sections.

• Create an osd_parser and remove from mdt and ost sections
• remove brw_stats from ost section
• Convert LustreCollectorError to use thiserror
• Move brw_stats_parser up a level
• Add TryFrom impl for &Target to TargetVariant

Fixes #40

Signed-off-by: Joe Grund jgrund@whamcloud.io

Demo

[root@ai400x-0a9c-vm00 ~]# /scratch/lustre_collector -f yaml | grep -A 50 'param: brw_stats'
      param: brw_stats
      target: MGS
      value:
        - name: pages
          unit: rpcs
          buckets: []
        - name: discont_pages
          unit: rpcs
          buckets: []
        - name: discont_blocks
          unit: rpcs
          buckets: []
        - name: dio_frags
          unit: ios
          buckets: []
        - name: rpc_hist
          unit: ios
          buckets: []
        - name: io_time
          unit: ios
          buckets: []
        - name: disk_iosize
          unit: ios
          buckets: []
- Target:
    BrwStats:
      kind: Mdt
      param: brw_stats
      target: ai400x2-MDT0000
      value:
        - name: pages
          unit: rpcs
          buckets: []
        - name: discont_pages
          unit: rpcs
          buckets: []
        - name: discont_blocks
          unit: rpcs
          buckets: []
        - name: dio_frags
          unit: ios
          buckets: []
        - name: rpc_hist
          unit: ios
          buckets: []
        - name: io_time
          unit: ios
          buckets: []
        - name: disk_iosize
          unit: ios
          buckets: []
- Target:
    BrwStats:
      kind: Ost
      param: brw_stats
      target: ai400x2-OST0000
      value:
        - name: pages
          unit: rpcs
          buckets:
            - name: 256
              read: 0
              write: 2
            - name: 512
              read: 0
              write: 0
            - name: 1024
              read: 0
              write: 736
        - name: discont_pages
          unit: rpcs
          buckets:
            - name: 0
              read: 0
              write: 738
        - name: discont_blocks
          unit: rpcs
          buckets:
            - name: 0
              read: 0
              write: 738
        - name: dio_frags
          unit: ios
          buckets:
            - name: 1
              read: 0
              write: 2
            - name: 2
              read: 0
              write: 0
            - name: 3
              read: 0
              write: 0
            - name: 4
              read: 0
              write: 736
        - name: rpc_hist
          unit: ios
          buckets:
            - name: 1
              read: 0
              write: 738
            - name: 2
              read: 0
              write: 736
--
      param: brw_stats
      target: ai400x2-OST0001
      value:
        - name: pages
          unit: rpcs
          buckets:
            - name: 1024
              read: 0
              write: 625
        - name: discont_pages
          unit: rpcs
          buckets:
            - name: 0
              read: 0
              write: 625
        - name: discont_blocks
          unit: rpcs
          buckets:
            - name: 0
              read: 0
              write: 625
        - name: dio_frags
          unit: ios
          buckets:
            - name: 4
              read: 0
              write: 625
        - name: rpc_hist
          unit: ios
          buckets:
            - name: 1
              read: 0
              write: 625
            - name: 2
              read: 0
              write: 625
            - name: 3
              read: 0
              write: 625
            - name: 4
              read: 0
              write: 625
        - name: io_time
          unit: ios
          buckets:
            - name: 1
              read: 0
              write: 621
            - name: 2
              read: 0
              write: 0