Uninstall notification can panic because of string concatination that is too long

[cmacknz]

This was reproduced on a Windows machine for the first 9.0 build candidate.

C:\code\EAF\Python>"\Program Files\Elastic\Agent\elastic-agent.exe" uninstall
Elastic Agent will be uninstalled from your system at C:\Program Files\Elastic\Agent. Do you want to continue? [Y/n]:Y
[====] Attempting to notify Fleet of uninstall  [1s] fatal error: string concatenation too long

goroutine 1 gp=0xc0000da000 m=5 mp=0xc000100008 [running]:
fatal error: unexpected signal during runtime execution
panic during panic
[signal 0xc0000005 code=0x1 addr=0xc92485 pc=0xcbd3e0]

runtime stack:
fatal error: unexpected signal during runtime execution
stack trace unavailable

C:\code\EAF\Python>

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[cmacknz]

This looks like another variation of #5952 but with a more specific error.