MIR: `PAIR n`, `UNPAIR n`, `GET n`, `UPDATE n`, `GET_AND_UPDATE: map` instructions

Context

Adds PAIR n, UNPAIR n, GET n, UPDATE n, and GET_AND_UPDATE variant for map.

The first 4 are related, so it makes sense to handle them together. GET_AND_UPDATE isn't exactly related, but is included anyway to save on overhead a bit.

Most of the diff is in tests.

Based on: !11194 (merged)

Part of: #6626 (closed)

Manually testing the MR

cargo test

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
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