Add IndexType and IndexMethod classes

[Tigrov]

Related PR

• Move index type constants to IndexType class db#920

Q	A
Is bugfix?	✔️/❌
New feature?	✔️
Breaks BC?	✔️/❌
Fixed issues

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.91%. Comparing base (8d44f35) to head (8b13965).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #374   +/-   ##
=========================================
  Coverage     98.91%   98.91%           
  Complexity      173      173           
=========================================
  Files            16       16           
  Lines           552      552           
=========================================
  Hits            546      546           
  Misses            6        6           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.