common/lru: add generic LRU implementation (#26162)

It seems there is no fully typed library implementation of an LRU cache.
So I wrote one. Method names are the same as github.com/hashicorp/golang-lru,
and the new type can be used as a drop-in replacement.

Two reasons to do this:

- It's much easier to understand what a cache is for when the types are right there.
- Performance: the new implementation is slightly faster and performs zero memory
   allocations in Add when the cache is at capacity. Overall, memory usage of the cache
   is much reduced because keys are values are no longer wrapped in interface.

eth/filters/filter_system.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/lru"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/bloombits"
 	"github.com/ethereum/go-ethereum/core/rawdb"
@@ -35,7 +36,6 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
-	lru "github.com/hashicorp/golang-lru"
 )
 
 // Config represents the configuration of the filter system.
@@ -77,21 +77,16 @@ type Backend interface {
 // FilterSystem holds resources shared by all filters.
 type FilterSystem struct {
 	backend   Backend
-	logsCache *lru.Cache
+	logsCache *lru.Cache[common.Hash, [][]*types.Log]
 	cfg       *Config
 }
 
 // NewFilterSystem creates a filter system.
 func NewFilterSystem(backend Backend, config Config) *FilterSystem {
 	config = config.withDefaults()
-
-	cache, err := lru.New(config.LogCacheSize)
-	if err != nil {
-		panic(err)
-	}
 	return &FilterSystem{
 		backend:   backend,
-		logsCache: cache,
+		logsCache: lru.NewCache[common.Hash, [][]*types.Log](config.LogCacheSize),
 		cfg:       &config,
 	}
 }
@@ -100,7 +95,7 @@ func NewFilterSystem(backend Backend, config Config) *FilterSystem {
 func (sys *FilterSystem) cachedGetLogs(ctx context.Context, blockHash common.Hash, number uint64) ([][]*types.Log, error) {
 	cached, ok := sys.logsCache.Get(blockHash)
 	if ok {
-		return cached.([][]*types.Log), nil
+		return cached, nil
 	}
 
 	logs, err := sys.backend.GetLogs(ctx, blockHash, number)

eth/gasprice/feehistory.go

@@ -56,7 +56,12 @@ type blockFees struct {
 	err     error
 }
 
-// processedFees contains the results of a processed block and is also used for caching
+type cacheKey struct {
+	number      uint64
+	percentiles string
+}
+
+// processedFees contains the results of a processed block.
 type processedFees struct {
 	reward               []*big.Int
 	baseFee, nextBaseFee *big.Int
@@ -270,13 +275,10 @@ func (oracle *Oracle) FeeHistory(ctx context.Context, blocks int, unresolvedLast
 					oracle.processBlock(fees, rewardPercentiles)
 					results <- fees
 				} else {
-					cacheKey := struct {
-						number      uint64
-						percentiles string
-					}{blockNumber, string(percentileKey)}
+					cacheKey := cacheKey{number: blockNumber, percentiles: string(percentileKey)}
 
 					if p, ok := oracle.historyCache.Get(cacheKey); ok {
-						fees.results = p.(processedFees)
+						fees.results = p
 						results <- fees
 					} else {
 						if len(rewardPercentiles) != 0 {

eth/gasprice/gasprice.go

@@ -23,13 +23,13 @@ import (
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/lru"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc"
-	lru "github.com/hashicorp/golang-lru"
 )
 
 const sampleNumber = 3 // Number of transactions sampled in a block
@@ -72,7 +72,8 @@ type Oracle struct {
 
 	checkBlocks, percentile           int
 	maxHeaderHistory, maxBlockHistory int
-	historyCache                      *lru.Cache
+
+	historyCache *lru.Cache[cacheKey, processedFees]
 }
 
 // NewOracle returns a new gasprice oracle which can recommend suitable
@@ -114,7 +115,7 @@ func NewOracle(backend OracleBackend, params Config) *Oracle {
 		log.Warn("Sanitizing invalid gasprice oracle max block history", "provided", params.MaxBlockHistory, "updated", maxBlockHistory)
 	}
 
-	cache, _ := lru.New(2048)
+	cache := lru.NewCache[cacheKey, processedFees](2048)
 	headEvent := make(chan core.ChainHeadEvent, 1)
 	backend.SubscribeChainHeadEvent(headEvent)
 	go func() {