core/rawdb: enhance database key construction

[cuiweixie]

goos: darwin
goarch: arm64
pkg: github.com/ethereum/go-ethereum/core/rawdb
cpu: Apple M4
                            │   old.txt   │               new.txt               │
                            │   sec/op    │   sec/op     vs base                │
StorageHistoryIndexBlockKey   32.64n ± 2%   19.09n ± 1%  -41.51% (p=0.000 n=10)

                            │   old.txt   │              new.txt               │
                            │    B/op     │    B/op     vs base                │
StorageHistoryIndexBlockKey   144.00 ± 0%   80.00 ± 0%  -44.44% (p=0.000 n=10)

                            │  old.txt   │              new.txt               │
                            │ allocs/op  │ allocs/op   vs base                │
StorageHistoryIndexBlockKey   2.000 ± 0%   1.000 ± 0%  -50.00% (p=0.000 n=10)