Add desired sharding keys for portfolio_management

Add desired sharding keys for feature category `portfolio_management`.

These tables have been identified as a [cell local tables](https://docs.gitlab.com/ee/development/database/multiple_databases.html#guidelines-on-choosing-between-gitlab_main_cell-and-gitlab_main_clusterwide-schema).
All cell local tables require a [sharding key](https://docs.gitlab.com/ee/development/database/multiple_databases.html#defining-a-sharding-key-for-all-cell-local-tables)
or a [desired sharding key](https://docs.gitlab.com/ee/development/database/multiple_databases.html#defining-a-desired_sharding_key-for-automatically-backfilling-a-sharding_key)

A desired sharding key has been automatically selected for these tables.
These keys were chosen as the desired sharding keys because the
table has a :belongs_to relationship to a table that itself has a `NOT NULL` sharding key.

We have assigned a random backend engineer from ~"group::product planning" to review these changes.

Please confirm that:

- each of these tables can be classified as cell local
- the selected desired sharding key is appropriate
- the backfill configuration for the desired sharding key is correct

When you are finished, please request a review from the database maintainer suggested by Danger.
If you have any questions or concerns, reach out to @tigerwnz, @DylanGriffith or @manojmj.

If you would like to go through similar merged MRs so as to gather an understanding on this topic, you
can use [this](https://gitlab.com/gitlab-org/gitlab/-/merge_requests?scope=all&state=merged&label_name[]=automation%3Agitlab-housekeeper-authored) link.

This change was generated by
[gitlab-housekeeper](https://gitlab.com/gitlab-org/gitlab/-/tree/master/gems/gitlab-housekeeper)

Changelog: other