[WIP] Introduce ResourceSupplier SPI

[sormuras]

Overview

Addresses part of #1555 by providing a new default extension handling @New and @Singleton annotations.

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes
• All continuous integration builds pass

[codecov]

Codecov Report

Merging #1672 into master will decrease coverage by 0.8%.
The diff coverage is 3.29%.

@@             Coverage Diff             @@
##             master   #1672      +/-   ##
===========================================
- Coverage     91.71%   90.9%   -0.81%     
- Complexity     4102    4105       +3     
===========================================
  Files           351     355       +4     
  Lines          9743    9834      +91     
  Branches        778     786       +8     
===========================================
+ Hits           8936    8940       +4     
- Misses          619     707      +88     
+ Partials        188     187       -1

Impacted Files	Coverage Δ	Complexity Δ
...it/jupiter/engine/extension/ExtensionRegistry.java	94.23% <ø> (ø)	23 <0> (ø)	⬇️
...ava/org/junit/platform/commons/util/FileUtils.java	0% <0%> (ø)	0 <0> (?)
.../junit/jupiter/api/extension/ResourceSupplier.java	0% <0%> (ø)	0 <0> (?)
...va/org/junit/jupiter/api/support/io/Temporary.java	0% <0%> (ø)	0 <0> (?)
...er/engine/extension/ResourceSupplierExtension.java	10.71% <10.71%> (ø)	3 <3> (?)
...jupiter/engine/execution/ExtensionValuesStore.java	91.17% <0%> (+1.47%)	21% <0%> (ø)	⬇️

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[sbrannen]

Closing due to suggested move to JUnit Pioneer.