Use enviornment variables for watcher cli args

[drGrove]

Using enviornment variable substitution for default cli args allows for modification of values via strategic merge patches instead of JSON6902. This reduces complexity of patches, allows for easier namespace overrides as well as a cleaner overlay

Changes

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you review them:

• [x] Has Docs included if any changes are user facing
• [x] Has Tests included if any functionality added or changed
• [x] Tested your changes locally (if this is a code change)
• [x] Follows the commit message standard
• [x] Meets the Tekton contributor standards (including functionality, content, code)
• [x] Has a kind label. You can add a comment on this PR that contains /kind <type>. Valid types are bug, cleanup, design, documentation, feature, flake, misc, question, tep
• [ ] Release notes block below has been updated with any user-facing changes (API changes, bug fixes, changes requiring upgrade notices or deprecation warnings)
• [ ] Release notes contain the string "action required" if the change requires additional action from users switching to the new release

Release Notes

[tekton-robot]

Hi @drGrove. Thanks for your PR.

I'm waiting for a tektoncd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[drGrove]

/kind cleanup

[enarha]

/ok-to-test

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: avinal, james-callahan

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/tektoncd/results/blob/main/OWNERS)~~ [avinal] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[khrm]

/kind misc