feat: Add URL encoding for S3 object keys

[Tnirpps]

S3 URL Encoding Fix

Problem

S3 API methods (GetObject, PutObject, etc.) failed with object keys containing special characters (spaces, Cyrillic, etc.) because they weren't being URL-encoded.
Bad URL, curl error: malformed input, url: https://mybucket.s3-some-site.awsornot.com/path/to/object with : spaces

Solution

Added two functions for proper S3 object key encoding, compatible with AWS SDK behavior:

• UrlEncodePathSegment() - encodes a single path segment, preserving RFC 3986 unreserved chars (-, _, ., ~) and S3-safe chars ($, &, ,, :, =, @)
• EncodeS3Key() - encodes S3 object key, preserving / as path separators

Implementation follows AWS SDK approach: aws-sdk-cpp/URI.cpp

Examples:

EncodeS3Key("folder/file with spaces.txt")  // → "folder/file%20with%20spaces.txt"
EncodeS3Key("folder/файл.txt")              // → "folder/%D1%84%D0%B0%D0%B9%D0%BB.txt"

Changes

• universal/http/url.hpp, url.cpp: New encoding functions
• universal/http/url_test.cpp: new tests
• libraries/s3api/s3api_methods.cpp: Apply EncodeS3Key() to all S3 methods