Add golang.org/x/tools modernize static analyzer and fix violations (#15946)

* Ran gopls modernize to fix everything

go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...

* Override rules_go provided dependency for golang.org/x/tools to v0.38.0.

To update this, checked out rules_go, then ran `bazel run //go/tools/releaser -- upgrade-dep -mirror=false org_golang_x_tools` and copied the patches.

* Fix buildtag violations and ignore buildtag violations in external

* Introduce modernize analyzer package.

* Add modernize "any" analyzer.

* Fix violations of any analyzer

* Add modernize "appendclipped" analyzer.

* Fix violations of appendclipped

* Add modernize "bloop" analyzer.

* Add modernize "fmtappendf" analyzer.

* Add modernize "forvar" analyzer.

* Add modernize "mapsloop" analyzer.

* Add modernize "minmax" analyzer.

* Fix violations of minmax analyzer

* Add modernize "omitzero" analyzer.

* Add modernize "rangeint" analyzer.

* Fix violations of rangeint.

* Add modernize "reflecttypefor" analyzer.

* Fix violations of reflecttypefor analyzer.

* Add modernize "slicescontains" analyzer.

* Add modernize "slicessort" analyzer.

* Add modernize "slicesdelete" analyzer. This is disabled by default for now. See https://go.dev/issue/73686.

* Add modernize "stringscutprefix" analyzer.

* Add modernize "stringsbuilder" analyzer.

* Fix violations of stringsbuilder analyzer.

* Add modernize "stringsseq" analyzer.

* Add modernize "testingcontext" analyzer.

* Add modernize "waitgroup" analyzer.

* Changelog fragment

* gofmt

* gazelle

* Add modernize "newexpr" analyzer.

* Disable newexpr until go1.26

* Add more details in WORKSPACE on how to update the override

* @nalepae feedback on min()

* gofmt

* Fix violations of forvar

beacon-chain/sync/initial-sync/blocks_fetcher_test.go

@@ -388,7 +388,7 @@ func TestBlocksFetcher_scheduleRequest(t *testing.T) {
 
 	t.Run("unblock on context cancellation", func(t *testing.T) {
 		fetcher := newBlocksFetcher(t.Context(), &blocksFetcherConfig{})
-		for i := 0; i < maxPendingRequests; i++ {
+		for range maxPendingRequests {
 			assert.NoError(t, fetcher.scheduleRequest(t.Context(), 1, blockBatchLimit))
 		}