feat: Drop strict mode in favor of leniency flags.

[ShogunPanda]

This PR drops completely the strict mode in favor of three new leniency flags.

[mcollina]

lgtm

does this impact the benchmarks at all?

[ShogunPanda]

Nope, nothing at all.

Before:

> llhttp@8.1.1 bench /Volumes/DATI/Users/Shogun/Programmazione/Work/NearForm/internal/llhttp
> ts-node bench/

url loose (C)
8192.00 mb | 2559.11 mb/s | 51604286.45 ops/sec | 3.20 s
url strict (C)
8192.00 mb | 2328.31 mb/s | 46950162.77 ops/sec | 3.52 s
http loose: "seanmonstar/httparse" (C)
8192.00 mb | 1690.68 mb/s | 2521771.31 ops/sec | 4.85 s
http strict: "seanmonstar/httparse" (C)
8192.00 mb | 1693.59 mb/s | 2526117.23 ops/sec | 4.84 s
http loose: "nodejs/http-parser" (C)
8192.00 mb | 1375.00 mb/s | 2772670.79 ops/sec | 5.96 s
http strict: "nodejs/http-parser" (C)
8192.00 mb | 1400.48 mb/s | 2824064.73 ops/sec | 5.85 s

After (consider that the new mode is equivalent to the old strict mode):

> llhttp@8.1.1 bench /Volumes/DATI/Users/Shogun/Programmazione/Work/NearForm/internal/llhttp
> ts-node bench/

url (C)
8192.00 mb | 2353.59 mb/s | 47460018.51 ops/sec | 3.48 s
http: "seanmonstar/httparse" (C)
8192.00 mb | 1699.92 mb/s | 2535553.77 ops/sec | 4.82 s
http: "nodejs/http-parser" (C)
8192.00 mb | 1393.77 mb/s | 2810517.62 ops/sec | 5.88 s

Are we good to merge and release?

[RafaelGSS]

It's missing the breaking change label, right? Also, would be great to have a PR description so people can look at it when evaluating llhttp 9

[davidbolvansky]

For people coming from old http_parser it would be good to write steps how to migrate to llhttp if they used STRICT=OFF in cmake.