mobilecoind: add tx_out_view_key_match api (#4016)

[holtzman]

see PR #4016 from @eranrund:

Motivation

We needed to have the ability to do view key matching on some txo data and we are already running mobilecoind, so instead of having to link in a lot of the mobilecoin Rust code, we added an endpoint to mobilecoind to do this.

We're using it and can confirm it works, and we also added a unit test for it.

We merged #4016 into a side branch of release/6.1 in our main repo so that it could receive a full scan by CI/CD via this PR before merging into the release/6.1 branch.

[github-actions]

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