Tel v2 schema for app-started payload requires 'configuration'

[cataphract]

What does this PR do?

Fixes app-started telemetry messages that don't include the "configuration" key. This key is required by the schema.

Motivation

Failing system tests: DataDog/system-tests#2785

Additional Notes

System tests started failing once DataDog/dd-trace-php#2757 was merged and telemetry messages were actually sent.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.45%. Comparing base (94bee0c) to head (d7779ae).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #543   +/-   ##
=======================================
  Coverage   70.45%   70.45%           
=======================================
  Files         208      208           
  Lines       28414    28414           
=======================================
  Hits        20020    20020           
  Misses       8394     8394           

Components	Coverage Δ
crashtracker	25.53% <ø> (ø)
datadog-alloc	98.73% <ø> (ø)
data-pipeline	50.00% <ø> (ø)
data-pipeline-ffi	0.00% <ø> (ø)
ddcommon	86.43% <ø> (ø)
ddcommon-ffi	75.29% <ø> (ø)
ddtelemetry	58.95% <ø> (ø)
ipc	84.13% <ø> (ø)
profiling	78.09% <ø> (ø)
profiling-ffi	56.76% <ø> (ø)
serverless	0.00% <ø> (ø)
sidecar	35.42% <ø> (ø)
sidecar-ffi	0.00% <ø> (ø)
spawn-worker	54.98% <ø> (ø)
trace-mini-agent	71.14% <ø> (ø)
trace-normalization	98.24% <ø> (ø)
trace-obfuscation	95.73% <ø> (ø)
trace-protobuf	77.16% <ø> (ø)
trace-utils	91.03% <ø> (ø)

[pr-commenter]

Benchmarks

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