Fixes part of #59: Translate binding adapter files to java [BLOCKED: #1514]

[miaboloix]

Explanation

Fixes part of #59: Translate binding adapter files to java

Because kt_android_library() is split into android_library and kt_jvm_library under the hood -- it has been difficult to get custom Binding Adapters in Kotlin to build with Bazel + databinding. The current workaround for this is to translate our binding adapter files to Java so that they can build using android_library(), which now supports databinding. See bazelbuild/rules_kotlin#346 and bazelbuild/bazel#2694

Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• The PR explanation includes the words "Fixes #bugnum: ..." (or "Fixes part of #bugnum" if the PR only partially fixes an issue).
• The PR follows the style guide.
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• The PR is made from a branch that's not called "develop".
• The PR is made from a branch that is up-to-date with "develop".
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[BenHenning]

Thanks @miaboloix! Generally LGTM, though there are a few lingering comment threads to resolve before merging into develop.

[anandwana001]

LGTM, Thanks @miaboloix

[BenHenning]

Thanks @miaboloix! Just had two nits that you can resolve once their corresponding requests are done. Please let me know if I need to clarify anything.