This PR is a simple refactoring that does four things:
- Renames test/policy_fee_tests.cpptotest/feerounder_tests.cpp.
- Renames policy/fees.{h,cpp}topolicy/fees/block_policy_estimator.{h,cpp}.
- Renames policy/fees_args.cpptopolicy/fees/block_policy_estimator_args.cpp.
- Modifies estimateSmartFeeto return the block height at which the estimate was made by adding abest_heightunsigned int value to theFeeCalculationstruct.
Motivation
In preparation for adding a new fee estimator, the fees directory is created so we can organize code into block_policy_estimator and mempool because
a) It would be clunky to add more code directly under fees.
b) Having policy/fees.{h,cpp} and policy/mempool.{h,cpp} would also be undesirable.
Therefore, it makes sense to structure the it as policy/fees/block_policy_estimator, policy/fees/mempool, etc.
Hence test file were also updated accordingly.
The current block height is also returned because later in #30157 we log the height at which each estimate is made (at the debug log category of fee estimation :) ). This feature is particularly useful for empirical data analysis.