fix: use async db in sim_round

[Fraser999]

Description

This PR changes the builder in line with the change in sim_round to use async DB functions for the preflight checks.

Without this, the tokio runtime would become deadlocked due to many calls to block_in_place(|| handle.block_on(f)). See the related ticket for further info.

NOTE: This also includes a version bump to rc 5

Related Issue

ENG-1944

Testing

• ad hoc testing via running a builder shows that this no longer locks up under load.
• make fmt passes
• make clippy passes
• make test passes

[Fraser999]

• fix: use async db in sim_round #237 👈 (View in Graphite)
• main

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