feat(sdk): add iterateParamPassStyle and itemPassStyle params to loop

[Tomcli]

Which issue is resolved by this Pull Request: Resolves #1058

Description of your changes: Add new sdk support for new pipelineloop syntax. Two new fields iterateParamPassStyle and itemPassStyle, both of which can be either inline (default value) or file will sit on the same spec level as parallelism. The initial implementation is sdk support only.

Environment tested:

• Python Version (use python --version):
• Tekton Version (use tkn version):
• Kubernetes Version (use kubectl version):
• OS (e.g. from /etc/os-release):

Checklist:

• [ ] The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[Tomcli]

cc @Udiknedormin

[Tomcli]

cc @Udiknedormin

[Tomcli]

/assign @yhwang

[Tomcli]

/hold need some minor changes

[Tomcli]

/unhold

[google-oss-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Tomcli, Udiknedormin, yhwang

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