refactor(ast,parser): use u32 for node spans

[Boshen]

The next PR will fix the jargon where Node = Span.

relates to #9

[github-actions]

Parser Benchmark Results

group                    main                                   pr
-----                    ----                                   --
parser/babylon.max.js    1.04    129.8±5.06ms    79.6 MB/sec    1.00    125.1±4.43ms    82.5 MB/sec
parser/d3.js             1.01     16.2±0.65ms    33.6 MB/sec    1.00     16.0±0.71ms    34.1 MB/sec
parser/lodash.js         1.05      4.7±0.21ms   108.9 MB/sec    1.00      4.5±0.24ms   113.8 MB/sec
parser/pdf.js            1.02      9.2±0.38ms    43.8 MB/sec    1.00      9.0±0.41ms    44.7 MB/sec
parser/typescript.js     1.03    130.0±4.89ms    74.0 MB/sec    1.00    126.0±5.54ms    76.4 MB/sec