Release candidate 2.0

[danielhuppmann]

Description of PR

This PR adds the highlights for release 2.0.0, removes deprecated methods, and brings in a few minor clean-up items.

[codecov]

Codecov Report

Merging #779 (3ff2cab) into main (68b6c47) will decrease coverage by 0.1%.
Report is 1 commits behind head on main.
The diff coverage is 95.8%.

@@           Coverage Diff           @@
##            main    #779     +/-   ##
=======================================
- Coverage   94.7%   94.7%   -0.1%     
=======================================
  Files         62      62             
  Lines       5997    5967     -30     
=======================================
- Hits        5683    5652     -31     
- Misses       314     315      +1     

Files Changed	Coverage Δ
pyam/core.py	94.7% <71.4%> (-0.3%)	⬇️
pyam/iiasa.py	89.7% <100.0%> (-0.1%)	⬇️
pyam/str.py	100.0% <100.0%> (ø)
pyam/utils.py	91.6% <100.0%> (ø)
tests/conftest.py	98.1% <100.0%> (-0.1%)	⬇️
tests/test_feature_validation.py	100.0% <100.0%> (ø)
tests/test_string.py	100.0% <100.0%> (ø)
tests/test_tutorials.py	89.4% <100.0%> (ø)

[danielhuppmann]

Successfully deployed on test-pypi (after several iterations) and installed locally