k8s container id detection

[brettmc]

update container detection to follow current best-practise, per bug report. we should check v1 then v2, and a few other updates I ripped off from java's implementation. adding tests for k8s and podman, and break inline content out into fixtures.

Fixes: open-telemetry/opentelemetry-php#1114

[codecov]

Codecov Report

Merging #191 (33dc028) into main (c8e79a8) will increase coverage by 0.26%.
The diff coverage is 92.30%.

❗ Current head 33dc028 differs from pull request most recent head 737ddab. Consider uploading reports for the commit 737ddab to get more accurate results

@@             Coverage Diff              @@
##               main     #191      +/-   ##
============================================
+ Coverage     28.60%   28.87%   +0.26%     
- Complexity      472      474       +2     
============================================
  Files            47       47              
  Lines          1755     1763       +8     
============================================
+ Hits            502      509       +7     
- Misses         1253     1254       +1     

Flag	Coverage Δ
7.4	52.68% <92.30%> (+0.38%)	⬆️
8.0	28.17% <92.30%> (+0.31%)	⬆️
8.1	28.24% <92.30%> (+0.31%)	⬆️
8.2	28.88% <92.30%> (+0.26%)	⬆️

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Files Changed	Coverage
src/ResourceDetectors/Container/src/Container.php	92.30%

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