feat: search archived wf by startat. Closes #2436

[whynowy]

Closes #2436

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I have written unit and/or e2e tests for my change. PRs without these are unlike to be merged.
• Optional. I've added My organization is added to the USERS.md.
• I've signed the CLA and required builds are green.

[whynowy]

Can not use k8s fields.ParseSelector() because it only supports 3 operators: =, == and !=.

[whynowy]

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@10a0789). Click here to learn what that means.
The diff coverage is 38.7%.

@@            Coverage Diff            @@
##             master    #2473   +/-   ##
=========================================
  Coverage          ?   11.25%           
=========================================
  Files             ?       73           
  Lines             ?    30878           
  Branches          ?        0           
=========================================
  Hits              ?     3476           
  Misses            ?    26932           
  Partials          ?      470

Impacted Files	Coverage Δ
persist/sqldb/null_workflow_archive.go	0% <0%> (ø)
persist/sqldb/workflow_archive.go	0% <0%> (ø)
server/workflowarchive/archived_workflow_server.go	62.92% <57.14%> (ø)

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[alexec]

so that date format - it's not international - can you fix that?

[alexec]

e.g. 18 Feb 2020

[whynowy]

[alexec]

LGTM.