perf(core/txpool/legacypool): use maps.Keys and maps.Copy #30091#2165

AnilChinchawale merged 1 commit intoXinFinOrg:dev-upgradeXinFinOrg/XDPoSChain:dev-upgradefrom

gzliudan:legacypool_cachegzliudan/XDPoSChain:legacypool_cacheCopy head branch name to clipboard