Finding better implementations of PostTag and PostCategory

[D-Sketon]

Check List

• I have already read Docs page.
• I have already searched existing issues.

Feature Request

I was analysing the flame graph and noticed that PostTag has a lot of overheads.

In fact, we can optimise these simple sets of binary relations with map and set.
I wrote a simple demo for this, and this is what I got by rewriting the PostTag:
8x many-posts
before

Cold processing
┌──────────────────────────────┬───────────────┐
│ (index)                      │ Cost time (s) │
├──────────────────────────────┼───────────────┤
│ Load Plugin/Scripts/Database │ '0.25s'       │
│ Process Source               │ '10.79s'      │
│ Render Posts                 │ '13.49s'      │
│ Render Files                 │ '13.64s'      │
│ Save Database                │ '1.21s'       │
│ Total time                   │ '39.38s'      │
└──────────────────────────────┴───────────────┘
Hot processing
┌──────────────────────────────┬───────────────┐
│ (index)                      │ Cost time (s) │
├──────────────────────────────┼───────────────┤
│ Load Plugin/Scripts/Database │ '2.14s'       │
│ Process Source               │ '7.03s'       │
│ Render Files                 │ '11.60s'      │
│ Save Database                │ '1.08s'       │
│ Total time                   │ '21.85s'      │
└──────────────────────────────┴───────────────┘
Another Cold processing
┌──────────────────────────────┬───────────────┐
│ (index)                      │ Cost time (s) │
├──────────────────────────────┼───────────────┤
│ Load Plugin/Scripts/Database │ '0.24s'       │
│ Process Source               │ '11.27s'      │
│ Render Posts                 │ '13.32s'      │
│ Render Files                 │ '13.74s'      │
│ Save Database                │ '1.00s'       │
│ Total time                   │ '39.56s'      │
└──────────────────────────────┴───────────────┘

after

Cold processing
┌──────────────────────────────┬───────────────┐
│ (index)                      │ Cost time (s) │
├──────────────────────────────┼───────────────┤
│ Load Plugin/Scripts/Database │ '0.25s'       │
│ Process Source               │ '6.50s'       │
│ Render Posts                 │ '9.32s'       │
│ Render Files                 │ '13.79s'      │
│ Save Database                │ '1.02s'       │
│ Total time                   │ '30.88s'      │
└──────────────────────────────┴───────────────┘
Hot processing
┌──────────────────────────────┬───────────────┐
│ (index)                      │ Cost time (s) │
├──────────────────────────────┼───────────────┤
│ Load Plugin/Scripts/Database │ '2.11s'       │
│ Process Source               │ '2.40s'       │
│ Render Files                 │ '8.04s'       │
│ Save Database                │ '1.01s'       │
│ Total time                   │ '13.56s'      │
└──────────────────────────────┴───────────────┘
Another Cold processing
┌──────────────────────────────┬───────────────┐
│ (index)                      │ Cost time (s) │
├──────────────────────────────┼───────────────┤
│ Load Plugin/Scripts/Database │ '0.24s'       │
│ Process Source               │ '6.44s'       │
│ Render Posts                 │ '9.20s'       │
│ Render Files                 │ '13.82s'      │
│ Save Database                │ '1.04s'       │
│ Total time                   │ '30.75s'      │

Others

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