Convert data in `blockchain-address` format to `oli-address` format

[ryscheng]

After we finish this https://github.com/opensource-observer/oss-directory/issues/472 we should try to convert more of our addresses to the new OLI format.

Since the #472 issue is written as an incremental addition (rather than a breaking schema change), we can write a transformation (as opposed to a migration), see here for a how-to https://github.com/opensource-observer/oss-directory?tab=readme-ov-file#running-a-one-off-transformation

This will allow us to do things more incrementally rather than force a breaking change now. It gives us more time to think about the open questions in this issue: https://github.com/opensource-observer/oss-directory/issues/474