Fix potential memory leak in Logger

[upsj]

loggers store a shared_ptr to an executor, but don't provide any access to it (this appears to be an oversight). When adding a logger containing an executor to this executor, we prevent both from being freed, since they create an ownership cycle:

{
    auto exec = ReferenceExecutor::create() // refcount 1
    auto logger = SomeLogger::create(exec); // refcount exec 2, refcount logger 1
    exec->add_logger(logger); // refcount exec 2, logger 2
} // refcount exec 1, logger 1, thus none of the two can be destroyed

Thus this PR removes the executor member and deprecates all corresponding constructors, prodiving replacements without the executor parameter.

[yhmtsai]

LGTM. Could you also put the small example of the cycle ownership in the description?
I am surprised at the current log implementation does not require any executor.
Is any implementation may require an executor from logger not linop?

[upsj]

In all logger events, you have access to either the executor or a PolymorphicObject with a corresponding executor, so this should not be a limitation.

[ginkgo-bot]

Note: This PR changes the Ginkgo ABI:

Functions changes summary: 1 Removed, 594 Changed (42528 filtered out), 17 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable

For details check the full ABI diff under Artifacts here

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
18 Code Smells

72.7% Coverage
0.7% Duplication

[codecov]

Codecov Report

Merging #1056 (0622251) into develop (b3b3b04) will decrease coverage by 0.02%.
The diff coverage is 86.48%.

@@             Coverage Diff             @@
##           develop    #1056      +/-   ##
===========================================
- Coverage    91.80%   91.77%   -0.03%     
===========================================
  Files          499      499              
  Lines        42968    42972       +4     
===========================================
- Hits         39446    39439       -7     
- Misses        3522     3533      +11     

Impacted Files	Coverage Δ
core/test/log/convergence.cpp	100.00% <ø> (ø)
core/test/log/stream.cpp	99.23% <ø> (ø)
reference/test/log/convergence.cpp	92.85% <ø> (ø)
include/ginkgo/core/log/convergence.hpp	73.68% <28.57%> (-26.32%)	⬇️
include/ginkgo/core/log/stream.hpp	50.00% <37.50%> (-50.00%)	⬇️
core/test/base/executor.cpp	89.16% <100.00%> (-0.04%)	⬇️
core/test/base/lin_op.cpp	91.66% <100.00%> (-0.06%)	⬇️
core/test/base/polymorphic_object.cpp	99.01% <100.00%> (-0.01%)	⬇️
core/test/log/logger.cpp	100.00% <100.00%> (ø)
core/test/log/record.cpp	100.00% <100.00%> (ø)
... and 6 more

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