Migrate to from database to declarative index

[rtclauss]

The existing operator uses a database for the index.

If you attempt to install the StockTrader operator on a cluster that has an OLM version of greater than v0.21.1 you will see failures when deploying the operator and you will see this in the logs somewhere:

Sqlite-based catalogs and their related subcommands are deprecated. Support for
them will be removed in a future release. Please migrate your catalog workflows
to the new file-based catalog format.

A workaround is to install version v0.21.1of OLM in your cluster:

operator-sdk olm install --version=v0.21.1

I believe this means we need to move to the declarative-style of operator index.

https://github.com/operator-framework/enhancements/blob/master/enhancements/declarative-index-config.md#deprecations
operator-framework/olm-docs#177
https://olm.operatorframework.io/docs/reference/file-based-catalogs/

[jwalcorn]

I made this move several months ago. See the bundle/README.md for details. Let me know if there's still any issue. Thanks.