feat: mempool: Reduce minimum replace fee from 1.25x to 1.1x (#10416)

However, we're leaving the default at 1.25x for backwards compatibility, for now.

Also:

1. Actually use the configured replace fee ratio.
2. Store said ratios as percentages instead of floats. 1.25, or 1+1/(2^2),
can be represented as a float. 1.1, or 1 + 1/(2 * 5), cannot.

fixes #10415

documentation/en/api-v0-methods.md

@@ -2879,7 +2879,7 @@ Response:
   ],
   "SizeLimitHigh": 123,
   "SizeLimitLow": 123,
-  "ReplaceByFeeRatio": 12.3,
+  "ReplaceByFeeRatio": 1.23,
   "PruneCooldown": 60000000000,
   "GasLimitOverestimation": 12.3
 }
@@ -3167,7 +3167,7 @@ Inputs:
     ],
     "SizeLimitHigh": 123,
     "SizeLimitLow": 123,
-    "ReplaceByFeeRatio": 12.3,
+    "ReplaceByFeeRatio": 1.23,
     "PruneCooldown": 60000000000,
     "GasLimitOverestimation": 12.3
   }

documentation/en/api-v1-unstable-methods.md

@@ -3816,7 +3816,7 @@ Response:
   ],
   "SizeLimitHigh": 123,
   "SizeLimitLow": 123,
-  "ReplaceByFeeRatio": 12.3,
+  "ReplaceByFeeRatio": 1.23,
   "PruneCooldown": 60000000000,
   "GasLimitOverestimation": 12.3
 }
@@ -4104,7 +4104,7 @@ Inputs:
     ],
     "SizeLimitHigh": 123,
     "SizeLimitLow": 123,
-    "ReplaceByFeeRatio": 12.3,
+    "ReplaceByFeeRatio": 1.23,
     "PruneCooldown": 60000000000,
     "GasLimitOverestimation": 12.3
   }