Test/support Python 3.11

[arcondello]

Add Python3.11 to CI tests.

In Python 3.11, accessing a Tempfile after the context has been exited raises a

ValueError: I/O operation on closed file.

This means that when we do something like

class LeapHybridCQMSampler:
    ...
    def sample_cqm(...):
        ...
        with cqm.to_file() as f:
            self.solver.sample_cqm(f, ...)

we get an error because sample_cqm() is non-blocking. To resolve it, we separate out the upload step. E.g.

with cqm.to_file() as f:
    sapi_problem_id = self.solver.upload_problem(f).result()  # blocking
self.solver.sample_cqm(sapi_problem_id, ...)

Also removed some large and slow integration tests.

[codecov[bot]]

Codecov Report

Merging #492 (a90fc12) into master (d37ff69) will decrease coverage by 3.17%. The diff coverage is 65.38%.

@@            Coverage Diff             @@
##           master     #492      +/-   ##
==========================================
- Coverage   90.87%   87.70%   -3.17%     
==========================================
  Files          24       24              
  Lines        1677     1676       -1     
==========================================
- Hits         1524     1470      -54     
- Misses        153      206      +53     

Impacted Files	Coverage Δ
dwave/system/samplers/leap_hybrid_sampler.py	72.38% <65.38%> (-5.35%)	:arrow_down:

... and 5 files with indirect coverage changes

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[arcondello]

The big coverage diff is because the integration tests aren't being run on the PR.