added map support for over writable configs

[axenteoctavian]

Reasoning behind the pull request

• Needed support for Map in over writable configs for enableRound.toml
• also cleaned some stuff in tests

Proposed changes

• Added support for Map to be overwritten by other map
• Added tests with real data from a toml file

Testing procedure

• uncomment and always use OverridableConfigTomlValues in cmd/node/config/prefs.toml
• test override map with real data from prefs.toml (similar examples in testscommon/toml/overwrite.toml)
• also test other over-writable values: int/float/bool/struct/slice etc - with good and bad data
• nodes should start normally with correct values and log what was overridden, otherwise not start

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?