feat: bastion replacement

[ebezzi]

Replace makefile rules for connecting to Postgres through the new SSM-enabled machines.

Note: due to how awscli works, it is not possible to launch the tunnel in the background without resorting to bash shenanigans (forking the process via &, killing the process via kill). Therefore, I made the following changes:

1. make db/tunnel/up now needs to be launched on a separate shell, and will not fork the process
2. make db/connect will need to be called after the tunnel is up
3. Instead of running make db/tunnel/down, it is sufficient to shut down the tunnel via CTRL-C.

[github-actions[bot]]

Deployment Summary

• backend_url: https://pr-7328-backend.rdev.single-cell.czi.technology
• backend_de_url: https://pr-7328-backend-de.rdev.single-cell.czi.technology
• backend_wmg_url: https://pr-7328-backend-wmg.rdev.single-cell.czi.technology
• frontend_url: https://pr-7328-frontend.rdev.single-cell.czi.technology
• delete_db_task_definition_arn: arn:aws:ecs:us-west-2:***:task-definition/dp-rdev-pr-7328-deletion:1
• migrate_db_task_definition_arn: arn:aws:ecs:us-west-2:***:task-definition/dp-rdev-pr-7328-migration:1

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.93%. Comparing base (db2cc47) to head (c20b57b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7328 +/- ## ========================================== - Coverage 92.93% 92.93% -0.01% ========================================== Files 194 194 Lines 16818 16818 ========================================== - Hits 15630 15629 -1 - Misses 1188 1189 +1 ``` | [Flag](https://app.codecov.io/gh/chanzuckerberg/single-cell-data-portal/pull/7328/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/chanzuckerberg/single-cell-data-portal/pull/7328/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg) | `92.93% <ø> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg#carryforward-flags-in-the-pull-request-comment) to find out more.

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