Implement dictionary overrides

[Adamantios]

Proposed changes

Adds support for dictionary overrides.
valory-xyz/trader#311 demonstrates how this can be used.

Fixes

n/a

Types of changes

What types of changes does your code introduce? (A breaking change is a fix or feature that would cause existing functionality and APIs to not work as expected.)
Put an x in the box that applies

• Non-breaking fix (non-breaking change which fixes an issue)
• Breaking fix (breaking change which fixes an issue)
• Non-breaking feature (non-breaking change which adds functionality)
• Breaking feature (breaking change which adds functionality)
• Refactor (non-breaking change which changes implementation)
• Messy (mixture of the above - requires explanation!)

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING doc
• I am making a pull request against the main branch (left side). Also you should start your branch off our main.
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have locally run services that could be impacted and they do not present failures derived from my changes
• Public-facing documentation has been updated with the changes affected by this PR. Even if the provided contents are not in their final form, all significant information must be included.
• Any backwards-incompatible/breaking change has been clearly documented in the upgrading document.

Further comments

n/a