feat: add rich diff by default

[cedricziel]

This PR improves the trace structure assertion mechanism by implementing a PHPUnit-style diff output for comparing expected and actual trace structures. This enhancement makes it significantly easier for developers to understand what went wrong when trace assertions fail.

Key Improvements

1. Visual Diff Output
   Added a unified diff format similar to PHPUnit's approach
   Clear visual indicators for additions (+) and removals (-)
   Proper indentation for nested structures
   Consistent formatting for complex trace structures
2. Human-Readable Formatting
   Span kinds are displayed as readable constants (e.g., KIND_SERVER instead of 2)
   Status codes are displayed as readable constants (e.g., STATUS_ERROR instead of 2)
   Improved formatting for status descriptions and other trace attributes
3. Recursive Comparison
   Implemented a recursive diffing algorithm that handles nested structures
   Detailed comparison of arrays, including both indexed and associative arrays
   Special handling for trace-specific data structures

Before/After Example

Before:

Expected Trace Structure:
Root Span: "root-span"
Kind: KIND_SERVER
Child Span: "child-span"
Attribute "attribute.three": "value3"

Actual Trace Structure:
Root Span: "root-span"
Kind: KIND_SERVER
Child Span: "child-span"
Missing Attribute: "attribute.three"

After:

--- Expected Trace Structure
+++ Actual Trace Structure
@@ @@
Array (
  [0] => Array (
    ['name'] => "root-span"
    ['kind'] => KIND_SERVER
    ['children'] => Array (
      [0] => Array (
        ['name'] => "child-span"
        ['attributes'] => Array (
        - ['attribute.three'] => "value3"
        )
      )
    )
  )
)

Example with multiple root spans

--- Expected Trace Structure
+++ Actual Trace Structure
@@ @@
Array (
  [0] => Array (
    ['name'] => "root-span-1"
    ['kind'] => KIND_SERVER
    ['attributes'] => Array (
    - ['attribute.one'] => "expected-value-1"
    + ['attribute.one'] => "actual-value-1"
    )
  )
  [1] => Array (
    ['name'] => "root-span-2"
    ['kind'] => KIND_CLIENT
    ['attributes'] => Array (
    - ['attribute.two'] => 24
    + ['attribute.two'] => 42
    - ['attribute.three'] => true
    )
  )
)

[codecov]

Codecov Report

Attention: Patch coverage is 79.66102% with 36 lines in your changes missing coverage. Please review.

Project coverage is 81.88%. Comparing base (ea137c0) to head (22553f3).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
.../Test/src/Fluent/TraceAssertionFailedException.php	73.00%	27 Missing ⚠️
...rc/Utils/Test/src/TraceStructureAssertionTrait.php	88.31%	9 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #346      +/-   ##
============================================
+ Coverage     79.45%   81.88%   +2.43%     
- Complexity     1772     1806      +34     
============================================
  Files           137      137              
  Lines          7568     7640      +72     
============================================
+ Hits           6013     6256     +243     
+ Misses         1555     1384     -171     

Flag	Coverage Δ
Aws	92.24% <ø> (ø)
Context/Swoole	0.00% <ø> (ø)
Instrumentation/CakePHP	20.27% <ø> (ø)
Instrumentation/CodeIgniter	73.77% <ø> (ø)
Instrumentation/Curl	90.42% <ø> (ø)
Instrumentation/Doctrine	93.25% <ø> (ø)
Instrumentation/ExtAmqp	89.26% <ø> (ø)
Instrumentation/ExtRdKafka	86.23% <ø> (ø)
Instrumentation/Guzzle	69.51% <ø> (ø)
Instrumentation/HttpAsyncClient	78.31% <ø> (ø)
Instrumentation/IO	70.68% <ø> (ø)
Instrumentation/Laravel	64.07% <ø> (ø)
Instrumentation/MongoDB	74.28% <ø> (ø)
Instrumentation/MySqli	95.81% <ø> (ø)
Instrumentation/OpenAIPHP	87.31% <ø> (ø)
Instrumentation/PDO	90.15% <ø> (ø)
Instrumentation/Psr14	77.14% <ø> (ø)
Instrumentation/Psr15	89.41% <ø> (ø)
Instrumentation/Psr16	97.56% <ø> (ø)
Instrumentation/Psr18	77.77% <ø> (ø)
Instrumentation/Psr3	59.49% <ø> (ø)
Instrumentation/Psr6	97.67% <ø> (ø)
Instrumentation/Slim	86.30% <ø> (ø)
Instrumentation/Symfony	84.93% <ø> (ø)
Instrumentation/Yii	77.68% <ø> (ø)
Logs/Monolog	100.00% <ø> (ø)
Propagation/ServerTiming	100.00% <ø> (ø)
Propagation/TraceResponse	100.00% <ø> (ø)
ResourceDetectors/Azure	91.66% <ø> (ø)
ResourceDetectors/Container	93.02% <ø> (ø)
Sampler/RuleBased	33.51% <ø> (ø)
Shims/OpenTracing	92.45% <ø> (ø)
Symfony	87.81% <ø> (ø)
Utils/Test	88.09% <79.66%> (+17.60%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...rc/Utils/Test/src/TraceStructureAssertionTrait.php	89.80% <88.31%> (-0.80%)	⬇️
.../Test/src/Fluent/TraceAssertionFailedException.php	77.85% <73.00%> (+16.20%)	⬆️

... and 3 files with indirect coverage changes

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[cedricziel]

@brettmc this one is ready as well.