Update release, kurtosis etc to use `nimbus`

[arnetheduck]

nimbus offers a superset of the nimbus_execution_client functionality and should be used for release binaries etc..

Where relevant, nimbus executionClient (or nimbus execution_client - both work, need to pick one) replace the existing nimbus_execution_client.

[advaita-saha]

Need to change EF/ethpandaops client builder first
And our docker images, before moving ahead with these changes

[advaita-saha]

Also please let's do nimbus execution_client, for consistency
And also because camel case in this scenario look really weird ( atleast in my eyes )

[arnetheduck]

we recommend it for trustedNodeSync - I don't have any particular opinion beyond using the same for both