Make rosetta construction/metadata return the correct default fee

[jspada]

* Use compile-time constant rather than hardcoded

This PR fixes an issue with rosetta construction/metadata where it returns a hardcoded default transaction fee.

Instead of returning the hardcoded fee we now return the default fee from the compile-time config Mina_compile_config.default_transaction_fee

The test agent (test-agent/agent.ml) does not have any test cases using the default fee so required no updates.

Testing:

Prior to these changes construction/metadata returns a hardcoded fee of 1 Mina. After the change it returns the value from the compile-time constant in one of the .mlh files.

Rosetta will now return the default fee depending on the build profile used. For example, for the production build profile, the default_transaction_fee from src/config/amount_defaults/realistic.mlh will be returned.

This can be tested either with the test script src/app/rosetta/test-curl/con_metadata.sh or by using mina_ledger_wallet send-payment and seeing that the correct default fee is obtained.

Checklist:

• Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• All tests pass (CI will check this if you didn't)
• Serialized types are in stable-versioned modules
• Does this close issues? List them:

Closes #8100

[deepthiskumar]

Did you mean to add minimum_user_command_fee (as per the PR description)?

[jspada]

Thanks. As far as I understand, this is to be done in a separate PR as it would not be a hotfix (see #8086).

[bkase]

!ci-build-me

[bkase]

!approved-for-mainnet

[mrmr1993]

!ci-build-me