Update report_timing() to support context manager API

[jsiirola]

Fixes # .

Summary/Motivation:

This updates the old report_timing() function so that it can be used as a context manager. When used as a context manager, it will undo the changes that it made to the timing loggers upon exit from the context. Among other things, this prevents side effects from enabling report_timing in model.create_instance() and makes it easier to exercise the timing statements in the transformations and writers.

This also adds a test that exercises the timing reporting for the NLv2 (which was the original motivation)

Changes proposed in this PR:

• Convert report_timing() to support use as a context manager
• Use report_timing() context manager in Model.create_instance()
• Add test exercising timing in NLv2 writer

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (15a7bff) 87.96% compared to head (b12ce95) 87.97%.

Files	Patch %	Lines
pyomo/core/base/PyomoModel.py	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3039      +/-   ##
==========================================
+ Coverage   87.96%   87.97%   +0.01%     
==========================================
  Files         770      770              
  Lines       90162    90178      +16     
==========================================
+ Hits        79310    79336      +26     
+ Misses      10852    10842      -10     

Flag	Coverage Δ
linux	85.30% <98.11%> (+0.01%)	⬆️
osx	75.12% <98.11%> (+0.01%)	⬆️
other	85.48% <98.11%> (+0.01%)	⬆️
win	82.55% <98.11%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

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