Spring extension

[ledoyen]

Adds support for composable extensions.
Adds support for Spring through a dedicated module.

[codecov]

Codecov Report

Merging #6 into master will decrease coverage by 0.12%.
The diff coverage is 95.26%.

@@            Coverage Diff             @@
##           master       #6      +/-   ##
==========================================
- Coverage   95.01%   94.89%   -0.13%     
==========================================
  Files          90      102      +12     
  Lines        1444     1683     +239     
  Branches      188      212      +24     
==========================================
+ Hits         1372     1597     +225     
- Misses         46       54       +8     
- Partials       26       32       +6

Impacted Files	Coverage Δ
.../glacio/running/runtime/io/FlatteningIterator.java	100% <ø> (ø)	⬆️
...cio/running/runtime/convert/ToNumberConverter.java	100% <ø> (ø)	⬆️
...thub/fridujo/glacio/running/api/convert/Value.java	100% <ø> (ø)	⬆️
...unit/engine/descriptor/GlacioEngineDescriptor.java	100% <ø> (ø)	⬆️
...fridujo/glacio/running/runtime/RuntimeOptions.java	100% <100%> (ø)	⬆️
...unning/runtime/extension/ExtensionContextImpl.java	100% <100%> (ø)
.../fridujo/glacio/junit/engine/GlacioTestEngine.java	100% <100%> (ø)	⬆️
...jo/glacio/running/runtime/extension/StoreImpl.java	100% <100%> (ø)
...junit/engine/descriptor/StepDescriptorFactory.java	100% <100%> (ø)	⬆️
...t/engine/discovery/IsGlacioConfigurationClass.java	100% <100%> (ø)
... and 36 more

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