🚀 Make IP validation 2x faster

[sadfun]

Description

This commit makes c.IP() and c.IPs() faster, especially when IP validation is enabled.

Benchmarks on my machine after this commit:

> go test -v -run=ctx_test.go -bench=Benchmark_Ctx_IP
goos: darwin
goarch: amd64
pkg: github.com/gofiber/fiber/v2
cpu: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
Benchmark_Ctx_IPs
Benchmark_Ctx_IPs-12                                             5892488               202.4 ns/op            48 B/op          1 allocs/op
Benchmark_Ctx_IPs_v6
Benchmark_Ctx_IPs_v6-12                                          3978466               302.2 ns/op           128 B/op          1 allocs/op
Benchmark_Ctx_IPs_With_IP_Validation
Benchmark_Ctx_IPs_With_IP_Validation-12                          4453332               268.4 ns/op            48 B/op          1 allocs/op
Benchmark_Ctx_IPs_v6_With_IP_Validation
Benchmark_Ctx_IPs_v6_With_IP_Validation-12                       2458620               488.3 ns/op           128 B/op          1 allocs/op
Benchmark_Ctx_IP_With_ProxyHeader
Benchmark_Ctx_IP_With_ProxyHeader-12                            24604593                48.82 ns/op            0 B/op          0 allocs/op
Benchmark_Ctx_IP_With_ProxyHeader_and_IP_Validation
Benchmark_Ctx_IP_With_ProxyHeader_and_IP_Validation-12          12709902                93.63 ns/op            0 B/op          0 allocs/op
Benchmark_Ctx_IP
Benchmark_Ctx_IP-12                                             27120162                43.37 ns/op            8 B/op          1 allocs/op

Before this commit:

> go test -v -run=ctx_test.go -bench=Benchmark_Ctx_IP
goos: darwin
goarch: amd64
pkg: github.com/gofiber/fiber/v2
cpu: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz
Benchmark_Ctx_IPs
Benchmark_Ctx_IPs-12                                             4376821               265.9 ns/op            48 B/op          1 allocs/op
Benchmark_Ctx_IPs_v6
Benchmark_Ctx_IPs_v6-12                                          2381112               503.9 ns/op           256 B/op          4 allocs/op
Benchmark_Ctx_IPs_With_IP_Validation
Benchmark_Ctx_IPs_With_IP_Validation-12                          2151280               495.0 ns/op           112 B/op          4 allocs/op
Benchmark_Ctx_IPs_v6_With_IP_Validation
Benchmark_Ctx_IPs_v6_With_IP_Validation-12                       1527709               781.4 ns/op           320 B/op          7 allocs/op
Benchmark_Ctx_IP_With_ProxyHeader
Benchmark_Ctx_IP_With_ProxyHeader-12                            24476161                48.81 ns/op            0 B/op          0 allocs/op
Benchmark_Ctx_IP_With_ProxyHeader_and_IP_Validation
Benchmark_Ctx_IP_With_ProxyHeader_and_IP_Validation-12           5742741               208.6 ns/op            32 B/op          2 allocs/op
Benchmark_Ctx_IP
Benchmark_Ctx_IP-12                                             27599205                43.04 ns/op            8 B/op          1 allocs/op

Type of change

• [+] New feature (non-breaking change which adds functionality)

Checklist:

• [+] I have performed a self-review of my own code
• [+] I have commented my code, particularly in hard-to-understand areas
• [+] I have added tests that prove my fix is effective or that my feature works
• [+] New and existing unit tests pass locally with my changes
• [+] I tried to make my code as fast as possible with as few allocations as possible
• [+] For new code I have written benchmarks so that they can be analyzed and improved

[efectn]

Can you create a PR for https://github.com/gofiber/utils

[efectn]

Please add some benchmarks and tests for ips like other utils.