Fixes#1710
The `If-Match` and `If-None-Match` precondition header values represent object ETags. ETags are generally quoted; however, S3 evaluates precondition headers equivalently whether the ETag is quoted or not, comparing only the underlying value and ignoring the quotes if present.
The new implementation trims quotes from the ETag in both the input precondition header and the object metadata, ensuring that comparisons are performed purely on the ETag value and are insensitive to quoting.
Closes#1346
`GetObject` and `HeadObject` return the `x-amz-tagging-count` header in the response, which specifies the number of tags associated with the object. This was already supported for `GetObject`, but missing for `HeadObject`. This implementation adds support for `HeadObject` in `azure` and `posix` and updates the integration tests to cover this functionality for `GetObject`.
All the integration tests used to be in a single file, which had become large, messy, and difficult to maintain. These changes split `tests.go` into multiple files, organized by logical test groups.
