Fix TotalLost type

[spe-dev]

The TotalLost field is defined as an uint32. But RFC 3550 mentions that the field can be set with negative values as it's a int24. To avoid bit manipulation in each apps that use pion, this PR do the job during Marshal/Unmarshal funcs.
Ref: https://datatracker.ietf.org/doc/html/rfc3550 Section 6.4 & A.3

[codecov]

Codecov Report

Merging #126 (5f40168) into master (ad1dcea) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #126      +/-   ##
==========================================
+ Coverage   76.28%   76.37%   +0.09%     
==========================================
  Files          21       21              
  Lines        2353     2362       +9     
==========================================
+ Hits         1795     1804       +9     
  Misses        461      461              
  Partials       97       97              

Flag	Coverage Δ
go	76.37% <100.00%> (+0.09%)	⬆️
wasm	76.37% <100.00%> (+0.09%)	⬆️

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Impacted Files	Coverage Δ
reception_report.go	100.00% <100.00%> (ø)

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[Sean-Der]

Changing this will cause the following packages to not compile, so I think it is worth a /v2 ! Great timing also, we can move pion/webrtc to the new version for 3.2.0

• Galene
• ion-sfu
• LiveKit

[enobufs]

We could potentially get around the breaking change by adding two helper methods to ReceiptionReport:

func (*ReceptionReport) SetTotalLostInt32(totalLost int32) {...}
func (*ReceptionReport) TotalLostInt32() int32 {...}

2c.