Merge bitcoin/bitcoin#27914: feerate: For GetFeePerK() return nSatoshisPerK instead of round trip through GetFee

11d6500 feerate: For GetFeePerK() return nSatoshisPerK instead of round trip through GetFee (Andrew Chow)

Pull request description:

  Returning the sats/kvb does not need to round trip through GetFee(1000) since the feerate is already stored as sats/kvb.

  Fixes #27913, although this does bring up a larger question of how we should handle such large feerates in fuzzing.

ACKs for top commit:
  furszy:
    Code ACK 11d6500

Tree-SHA512: bec1a0d4b572a0c810cf7eb4e97d729d67e96835c2d576a909f755b053a9707c2f1b3df9adb8f08a9c4d310cdbb8b1e1b42b9c004bd1ade02a07d8ce9e902138

Author: fanquake

src/policy/feerate.h

@@ -62,7 +62,7 @@ class CFeeRate
     /**
      * Return the fee in satoshis for a vsize of 1000 vbytes
      */
-    CAmount GetFeePerK() const { return GetFee(1000); }
+    CAmount GetFeePerK() const { return nSatoshisPerK; }
     friend bool operator<(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK < b.nSatoshisPerK; }
     friend bool operator>(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK > b.nSatoshisPerK; }
     friend bool operator==(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK == b.nSatoshisPerK; }