added tree and btree data structure in rust lang

[rohansen856]

Please check all that apply.

This PR is for:

• [x] Algorithm
• [ ] Cheatsheet
• [ ] Resource
• [ ] Other

Title for the Algorithm/Cheat-Sheet/Resource: [Title here]

Programming Language: [Language here]

• [x] Have you implemented it on your local machine or any online compiler?
• [x] There is the main( ) function to run the program and all the inputs which are being taken are clearly printed on the console or well commented in the file.
• [x] Filename is self-explanatory or there is Readme.md file explaining the necessary details of the algorithm.

P.S. Failing to update the PR in 10 days on requested changes will be marked outdated and closed.