add option to choose prepend/append patch items to list in merge

[Shell32-Natsu]

fix #2907

• From v3.8.0, strategic merge patches are changed from prepending items to appending(Starting in v3.8.0, strategic merge patches append to arrays (earlier versions prepend) #2907). This PR is changing back to the original behavior for strategic merge patches. Other places that use kyaml.merge2.Merge are still keeping appending.
• The API merge2.Merge and merge2.MergeStrings have a new parameter mergeOptions yaml.MergeOptions
  • yaml.MergeOptions has a member ListIncreaseDirection which can be MergeOptionsListAppend and MergeOptionsListPrepend.
  • If the ListIncreaseDirection is not set when create yaml.MergeOptions struct, it will be MergeOptionsListAppend by default.

[k8s-ci-robot]

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[Shell32-Natsu]

/cc @monopole

[monopole]

/lgtm

thanks!