[crashtracker] Send pid to the receiver

[danielsn]

What does this PR do?

Sends the PID to the receiver from the crashing process

Motivation

Currently, we use getppid, which only works because the receiver is the child of the crashing process. If we want to have a sidecar receiver, we'll need to know the actual pid.

Additional Notes

Anything else we should know when reviewing?

How to test the change?

Describe here in detail how the change can be validated.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 3.70370% with 26 lines in your changes missing coverage. Please review.

Project coverage is 69.61%. Comparing base (fc6e92b) to head (7cc7935).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #483      +/-   ##
==========================================
- Coverage   69.67%   69.61%   -0.07%     
==========================================
  Files         199      199              
  Lines       26606    26631      +25     
==========================================
  Hits        18539    18539              
- Misses       8067     8092      +25     

Components	Coverage Δ
crashtracker	17.17% <3.70%> (-0.30%)	⬇️
datadog-alloc	98.63% <ø> (-0.14%)	⬇️
data-pipeline	51.30% <ø> (ø)
data-pipeline-ffi	0.00% <ø> (ø)
ddcommon	85.97% <ø> (ø)
ddcommon-ffi	74.15% <ø> (ø)
ddtelemetry	56.37% <ø> (ø)
ipc	84.66% <ø> (ø)
profiling	79.13% <ø> (ø)
profiling-ffi	59.53% <ø> (ø)
serverless	0.00% <ø> (ø)
sidecar	36.26% <ø> (ø)
sidecar-ffi	0.00% <ø> (ø)
spawn-worker	54.98% <ø> (ø)
trace-mini-agent	69.36% <ø> (ø)
trace-normalization	97.79% <ø> (ø)
trace-obfuscation	95.73% <ø> (ø)
trace-protobuf	24.52% <ø> (ø)
trace-utils	90.79% <ø> (ø)

[r1viollet]

LGTM
This seems like something interesting to add tests to.