Add Chart image baking

[inteon]

Adds helm-tool images extract values.yaml -p paths.json and helm-tool images bake chart.tgz -p paths.json commands.

These commands can be used to "bake" the _defaultReference values, adding digests for tag-only image references.

TODO: make sure YAML comments are preserved.

[cert-manager-prow]

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[cert-manager-prow]

PR needs rebase.

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[maelvls]

We could replace gopkg.in/yaml.v3 with goccy/go-yaml package, which supports keeping comments and empty newlines, e.g.,

✦ $ ycat /dev/stdin <<EOF
foo: bar

# A comment
bar:foo

# Some extraneous newlines that should be kept as-is



# end of file
EOF
 1 | foo: bar
 2 |
 3 | # A comment
 4 | bar:foo
 5 |
 6 | # Some extraneous newlines that should be kept as-is
 7 |
 8 |
 9 |
10 | # end of file
11 |

Note that we will need to decode YAML into an AST instead of decoding it to a Go struct (otherwise, we will lose the comments and newlines and such). Goccy probably has helper funcs to modify the AST, then we can encode it back to YAML.