fix: Add `is_finished` and correct `is_empty` semantics in `RequestQueueClient` #735

Job	Run time
PR title check	3s
Checks / Package check	32s
Checks / Spell check	8s
Checks / Actions lint check	32s
Checks / Doc check / Docs check	1m 49s
Checks / Lint check / Lint check (3.12)	30s
Checks / Lint check / Lint check (3.14)	30s
Checks / Lint check / Lint check (3.10)	29s
Checks / Type check / Type check (3.11)	33s
Checks / Type check / Type check (3.14)	35s
Checks / Type check / Type check (3.12)	44s
Checks / Type check / Type check (3.13)	38s
Checks / Lint check / Lint check (3.11)	31s
Checks / Lint check / Lint check (3.13)	33s
Checks / Type check / Type check (3.10)	32s
Checks / Unit tests / Unit tests (windows-latest, 3.10)	7m 0s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.12)	5m 30s
Checks / Unit tests / Unit tests (macos-latest, 3.11)	3m 38s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.11)	4m 59s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.13)	5m 8s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.14)	3m 36s
Checks / Unit tests / Unit tests (macos-latest, 3.12)	4m 20s
Checks / Unit tests / Unit tests (windows-latest, 3.11)	6m 48s
Checks / Unit tests / Unit tests (macos-latest, 3.13)	3m 28s
Checks / Unit tests / Unit tests (macos-latest, 3.10)	6m 44s
Checks / Unit tests / Unit tests (windows-latest, 3.12)	6m 47s
Checks / Unit tests / Unit tests (windows-latest, 3.14)	5m 18s
Checks / Unit tests / Unit tests (macos-latest, 3.14)	3m 56s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.10)	5m 22s
Checks / Unit tests / Unit tests (windows-latest, 3.13)	5m 31s
	1h 26m 44s

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