Stabilize the ordering of initContainers

[EronWright]

Proposed changes

This PR is a breaking API change to ensure that a workspace's built-in init containers (bootstrap, fetch) are declared before any extra init containers found in the podTemplate.

Implementation-wise, the desired ordering is achieved with the $setElementOrder directive, as documented here:
https://github.com/kubernetes/design-proposals-archive/blob/main/cli/preserve-order-in-strategic-merge-patch.md

Migration Notes

If your application uses the podTemplate to inject init container(s), be aware that they'll run after the bootstrap and fetch containers. This means that the /share volume will be present, and your program code will have been downloaded, before your init container runs.

Related issues (optional)

Closes #774

[codecov]

Codecov Report

Attention: Patch coverage is 57.89474% with 16 lines in your changes missing coverage. Please review.

Project coverage is 53.19%. Comparing base (f42d305) to head (71d3a9a).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
operator/internal/controller/auto/utils.go	42.85%	8 Missing and 4 partials ⚠️
...r/internal/controller/auto/workspace_controller.go	76.47%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #923      +/-   ##
==========================================
+ Coverage   52.17%   53.19%   +1.02%     
==========================================
  Files          33       33              
  Lines        4556     4600      +44     
==========================================
+ Hits         2377     2447      +70     
+ Misses       1986     1960      -26     
  Partials      193      193              

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[pulumi-bot]

This PR has been shipped in release v2.1.0.