* Since We updated Euler-hs versions, some of the functions it used
  to export are not there anymore.

* Updates the code to reflect the new state of Euler-hs exports.

* ManagerSelector type in an older version of euler used to be a
  type synonym for "Text".

* This is now a newtype with a newtype constructor "ManagerSelector"
  from Euler.Types modules

* Wraps old useages with newtype constructor for correct type.

* The types changed in Aeson2 and beckn-shared-kernel

* Adds unordered-containers package in app/gateway's package.yaml
  to get the "HashMap" container.

* Changes types to "HashMap Text" where needed from "Map String"

…nges

* Removes now redundant imports after making the Aeson2 and
  beckn-shared-kernel changes in the previous commit

* makes "ambiguous-fields" a warning instead of an error.

* Adds the updated .cabal files for beckn-gateway and mock-registry.

* Updates the cabal files with the changes done in package.yaml
  files in the previous commits

* The cabal files were recently commited in the repository and are
  auto-generated by hpack tool, so we need to update them as we go.

* Updates flake.nix file with the following changes
  - update common repo to one that provides GHC 9.2.7 package set
  - updates shared-kernel to one that builds with GHC 9.2.7

* Updates the corresponding flake.lock file with the above changes.