Improved performance of power manifold creation and more

[mateuszbaran]

The ManifoldsBase.jl improvements that are needed for better performance of IPM.

Note: constraints are creating new PowerManifolds at every access and these constructors were type-unstable before these changes, creating significant slowdowns.

get_component(M::ProductManifold, p, i) with integers is still slow and I didn't really want to sprinkle everything with Base.@constprop :aggressive to try to improve it.

[kellertuer]

I trust that you know that this is faster ;)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.90%. Comparing base (2ac6a52) to head (50fcb95).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #197   +/-   ##
=======================================
  Coverage   99.90%   99.90%           
=======================================
  Files          31       31           
  Lines        3292     3294    +2     
=======================================
+ Hits         3289     3291    +2     
  Misses          3        3           

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