Add missing tests coverage to the s3-aws driver

We are currently missing tests coverage for the following cases:

• parameter parsing:
  • chunksize
  • multipartcopychunksize
  • multipartcopymaxconcurrency
  • multipartcopythresholdsize
  • maxrequestspersecond
  • maxretries
  • object ACL parameter should not be set when object ownership is enabled
• getParameterAsInt64:
  • conversion from string, int64, int, []byte,
  • min and max
• Writer:
  • s3Path(path) != *multi.Key - existing multi-part upload? this is a bigger issue, we should re-think whether we should be resuming multipart uploads at all.
• Stat:
  • fi.IsDir = true - never reached as we do not set Delimiter field
• Move:
  • lastByte = fileInfo.Size() - 1 - adjust lastbyte size
• URLFor
  • method != GET and method != HEAD (Post?)
• Walk is not covered at all
• WaltPararell:
  • fallback to Walk because parallel is not supported
  • path == ""
  • empty bucket
• Writer.Write:
  • old file is bigger than minChunkSize
• during multipart upload, if the last part is smaller than minpartsize, the file is re-uploaded, but what if the file is larger than 5GiB (i.e. max part size)?
• during flush, the pending and ready parts both have w.driver.ChunkSize size, and we do Commit() plus Close() - I check if here is going to be a data corruption here
• use multi-error in copy() func for pararell multi-part upload.
• resp, err := d.S3.ListObjectsV2WithContext(ctx, listObjectsV2Input) in the Delete() call - it should not treat error equal to resp.Contents == 0
• Stat call and all other that use ListObjectsV2Input should be precise when checking the output of the list as this only does a prefix match, and it should be matching on up to delimiter for the paths received. I have already added DirPartialPrefix test for the Stat() call
• chunk size should be smaller than 2x chunk size because of how flushPart() method works - if if int64(len(w.pendingPart)) < w.driver.ChunkSize { to wtedy pending i ready parts are concatenated which could result in double the size (well, almost)