fix: case insensitive comparison for RawPath to resolve incorrect rPath assignments

[iIIusi0n]

Go's standard url package doesn't assign RawPath if the escaped path is the same as the original path.
But for lower case escaped path, like "%ed%95%ab", it assumes they are different from escaped original path "%ED%95%AB".
So it assigns RawPath to "%ed%95%ab".
This has already been discussed in Go, but they said it works as intended.
net/http: RawPath shows inconsistent case-sensitive behaviour with percentage-encoded Unicode URI strings

Golang Gin checks the length of URL.RawPath when engine.UseRawPath is enabled.
If a percentage-encoded lower-case path is given, it redirects indefinitely. (Issue: #4034)

So add checks that compare RawPath and EscapedPath() with case insensitivity.