fix: Fix potential deadlocks in `SitemapRequestLoader` and `RequestManagerTandem` #455

Job	Run time
PR title check	6s
Code checks / Actions lint check	31s
Code checks / Spell check	7s
Doc checks / Doc checks / Docs check	1m 53s
Code checks / Type check / Type check (3.10)	25s
Code checks / Type check / Type check (3.11)	36s
Code checks / Type check / Type check (3.14)	35s
Code checks / Lint check / Lint check (3.13)	25s
Code checks / Lint check / Lint check (3.11)	32s
Code checks / Lint check / Lint check (3.10)	31s
Code checks / Type check / Type check (3.13)	31s
Code checks / Lint check / Lint check (3.12)	28s
Code checks / Type check / Type check (3.12)	35s
Code checks / Lint check / Lint check (3.14)	34s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.11)	4m 56s
Tests / Unit tests / Unit tests (windows-latest, 3.13)	6m 22s
Tests / Unit tests / Unit tests (windows-latest, 3.14)	5m 54s
Tests / Unit tests / Unit tests (macos-latest, 3.14)	4m 16s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.12)	5m 43s
Tests / Unit tests / Unit tests (windows-latest, 3.10)	6m 36s
Tests / Unit tests / Unit tests (macos-latest, 3.13)	5m 18s
Tests / Unit tests / Unit tests (macos-latest, 3.11)	6m 24s
Tests / Unit tests / Unit tests (macos-latest, 3.10)	8m 18s
Tests / Unit tests / Unit tests (windows-latest, 3.11)	9m 59s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.13)	4m 44s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.14)	3m 52s
Tests / Unit tests / Unit tests (macos-latest, 3.12)	8m 7s
Tests / Unit tests / Unit tests (ubuntu-latest, 3.10)	5m 23s
Tests / Unit tests / Unit tests (windows-latest, 3.12)	7m 15s
	1h 40m 56s

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