feat: support new field - RFC3339 in creationTimeStamp. Fixes #6906

[ziv-codefresh]

support RFC3339 new property in creationTimeStamp.

the issue was raised here - #6906
ive added additional property in creationTimeStamp that will represent this format, as @alexec suggested.

example of usage is:

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: steps-
spec:
  entrypoint: hello

  templates:
  - name: hello
    steps:
    - - name: h1
        template: whalesay
        arguments:
          parameters:
          - name: message
            value: "{{= workflow.creationTimestamp.RFC3339 }}"

  - name: whalesay
    inputs:
      parameters:
      - name: message
    container:
      image: docker/whalesay
      command: [cowsay]
      args: ["{{inputs.parameters.message}}"]

the output will be in RFC3339 format as expected.

• modified the unit test to check this property aswell.

[ziv-codefresh]

@simster7 sounds good, ive update the documentation.

[codecov]

Codecov Report

Merging #7044 (8537aca) into master (0758eab) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #7044      +/-   ##
==========================================
- Coverage   48.56%   48.56%   -0.01%     
==========================================
  Files         265      265              
  Lines       19294    19295       +1     
==========================================
- Hits         9371     9370       -1     
- Misses       8870     8872       +2     
  Partials     1053     1053              

Impacted Files	Coverage Δ
workflow/controller/operator.go	71.29% <100.00%> (+0.15%)	⬆️
cmd/argoexec/commands/emissary.go	50.35% <0.00%> (-1.44%)	⬇️
cmd/argo/commands/get.go	58.89% <0.00%> (-0.88%)	⬇️

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[ziv-codefresh]

@simster7 all the checks passed, if everything looks good from your hand i think we can merge it. thank you!