feat: add 'argocd-util cluster shards' command that prints shards statistics

[alexmt]

Signed-off-by: Alexander Matyushentsev [email protected]

PR implements argocd-util cluster shards that prints information about controller shards and number of resources per shard. Sample output:

argocd-util cluster shards
SHARD  RESOURCES COUNT
0      174912 (103%)
1      130555 (77%)
2      212047 (124%)
3      182060 (107%)
4      179262 (105%)
5      167561 (98%)
6      178011 (104%)
7      140308 (82%)

The command helps to understand if work is evenly shared across shards. The next step is to add --balance flag that calculates good shard for each cluster and ensure good balance for each shard.
e.g.

argocd-util cluster shards --balance

[codecov]

Codecov Report

Merging #6353 (ad98a1a) into master (3604a58) will decrease coverage by 0.12%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #6353      +/-   ##
==========================================
- Coverage   41.02%   40.90%   -0.13%     
==========================================
  Files         151      151              
  Lines       19954    20020      +66     
==========================================
+ Hits         8187     8189       +2     
- Misses      10639    10704      +65     
+ Partials     1128     1127       -1     

Impacted Files	Coverage Δ
cmd/argocd-util/commands/cluster.go	0.00% <0.00%> (ø)
util/kube/portforwarder.go	0.00% <0.00%> (ø)
util/settings/settings.go	46.75% <0.00%> (ø)
server/logout/logout.go	76.92% <0.00%> (+3.84%)	⬆️

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[kshamajain99]

LGTM