Use autoconfigured ClassLoader to load declarative config

[jack-berg]

Agent extensions aren't currently able to provide declarative configuration ComponentProvider SPI implementations because the agent requires a them to be loaded using a particular class loader.

This adds a new FileConfiguration#create overload which allows SpiHelper (which is based on a ClassLoader) to be specified, and updates AutoConfiguredOpenTelemetrySdkBuilder to call this new method.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.06%. Comparing base (39b2411) to head (16a4e67). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...nfigure/AutoConfiguredOpenTelemetrySdkBuilder.java	90.90%	1 Missing :warning:
...ension/incubator/fileconfig/FileConfiguration.java	92.30%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6725 +/- ## ========================================= Coverage 90.06% 90.06% - Complexity 6457 6463 +6 ========================================= Files 718 718 Lines 19511 19528 +17 Branches 1922 1923 +1 ========================================= + Hits 17572 17588 +16 Misses 1350 1350 - Partials 589 590 +1 ```

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