Auto merge of #106449 - GuillaumeGomez:rustdoc-gui-retry-mechanism, r=Mark-Simulacrum

Add retry mechanism for rustdoc GUI tests to reduce flakyness

Part of #93784.

I added 3 retries for failing GUI tests. An important note: if more than half of total tests fail, I don't retry because it's very likely not flakyness anymore at this point but a missing update after changes.

Author: bors