Improve ToString by 20%

[Fenny]

• Avoid unnecessary pointer dereferencing in convert.go#ToString
• Add all types in ToString tests and benchmarks

ok  	github.com/gofiber/utils/v2	2.314s	coverage: 75.4% of statements

**Before**
Benchmark_ToString-24            3499046               339.2 ns/op            96 B/op          6 allocs/op
Benchmark_ToString-24            3552510               336.8 ns/op            96 B/op          6 allocs/op
Benchmark_ToString-24            3589656               335.2 ns/op            96 B/op          6 allocs/op
Benchmark_ToString-24            3564043               337.8 ns/op            96 B/op          6 allocs/op
**After**
Benchmark_ToString-24            4211290               285.7 ns/op            96 B/op          6 allocs/op
Benchmark_ToString-24            4296464               282.5 ns/op            96 B/op          6 allocs/op
Benchmark_ToString-24            4279908               283.5 ns/op            96 B/op          6 allocs/op
Benchmark_ToString-24            4216419               283.5 ns/op            96 B/op          6 allocs/op

[gaby]

The previous benchmark had 10x more performance. https://github.com/gofiber/utils/actions/runs/7753577848/job/21145172120

Is this related to the change in the benchmark code?

[Fenny]

The previous benchmark had 10x more performance. https://github.com/gofiber/utils/actions/runs/7753577848/job/21145172120

Is this related to the change in the benchmark code?

Yes, see #62 (comment)