This patch adds FromFS function and lets you use the new go:embed directive to add the migration files to the binary.
Also, migration tests use an in memory FS impl instead of working with tmp directories.
Upstream merge
Add Session wrapper
With this patch we can now use gocqlx like:
```
session.Query(`SELECT * FROM struct_table`, nil).Get(&v)
```
instead of (old format):
```
gocqlx.Query(session.Query(`SELECT * FROM struct_table`), nil).Get(&v)
```
Signed-off-by: Michał Matczuk <michal@scylladb.com>
