Support dataframe.info() for getting the meta data of a dataframe

**Is your feature request related to a problem? Please describe.**
During daily usage, being able to know the general info about a dataframe is highly used. However, this is not yet supported in Mars.

**Describe the solution you'd like**
I'd like to use `df.info()` to fetch the metadata of a dataframe.

**Describe alternatives you've considered**
N/A

**Additional context**

No implementation files or tests are named in the issue. Start by locating Mars's dataframe API and existing metadata operations, then determine the expected behavior for df.info() from the request and attached example. Done means a dataframe can call df.info() and return the requested general metadata.

Written by the indexing model from the issue text.