🔉[RUMF-1423] Add debug log for retry issue

[bcaudan]

Motivation

A couple of orgs generated some telemetry errors where payload is undefined in:

browser-sdk/packages/core/src/transport/sendWithRetryStrategy.ts

Lines 73 to 74 in 34223e3

	const payload = state.queuedPayloads.first()
	send(payload, state, sendStrategy, {

Changes

• add some debug info when the first payload of the queue is not defined
• remove unnecessary resume after transport down debug log

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

Merging #1790 (81caf70) into main (34223e3) will decrease coverage by 0.04%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main    #1790      +/-   ##
==========================================
- Coverage   90.99%   90.94%   -0.05%     
==========================================
  Files         129      129              
  Lines        5039     5038       -1     
  Branches     1133     1133              
==========================================
- Hits         4585     4582       -3     
- Misses        454      456       +2     

Impacted Files	Coverage Δ
...ckages/core/src/transport/sendWithRetryStrategy.ts	98.83% <50.00%> (-1.17%)	⬇️
packages/core/src/transport/batch.ts	93.02% <0.00%> (-1.17%)	⬇️

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