Fix EigenGate equality

[daxfohl]

Fixes #7052. Also fixes #6764.

EigenGates of the same class generally differ only by the phases that they apply to each eigenspace. Therefore their _value_equality_values_ can be determined uniquely by calculating these phases. This is both faster (no need to calculate the period or canonical exponent) and more robust (exponentiation of phases is accounted for) than the existing implementation. The simplification also allows it to handle large global shifts that cause division-by-zero errors in period calculations (#6764). Additionally, many different edge cases with symbolic exponents are easier to identify and account for.

This also allows us to get rid of some superfluous _value_equality_values_ implementations in subclasses, except where the eigenspaces themselves are changeable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.17%. Comparing base (8f2f198) to head (5c13c13).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7057   +/-   ##
=======================================
  Coverage   98.17%   98.17%           
=======================================
  Files        1089     1089           
  Lines       95232    95199   -33     
=======================================
- Hits        93495    93463   -32     
+ Misses       1737     1736    -1     

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