fix: Add `is_finished` and align `is_empty` semantics in `ApifyRequestQueueClient` #842

Job	Run time
PR title check	4s
Checks / Lint check / Lint check (3.11)	15s
Checks / Lint check / Lint check (3.14)	15s
Checks / Lint check / Lint check (3.12)	17s
Checks / Doc check / Docs check	1m 6s
Checks / Lint check / Lint check (3.13)	13s
Checks / Type check / Type check (3.11)	11s
Checks / Spell check	6s
Checks / Package check	25s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.13)	1m 14s
Checks / Unit tests / Unit tests (windows-latest, 3.13)	2m 0s
Checks / Type check / Type check (3.13)	16s
Checks / Type check / Type check (3.14)	16s
Checks / Type check / Type check (3.12)	16s
Checks / Unit tests / Unit tests (windows-latest, 3.14)	1m 39s
Checks / Unit tests / Unit tests (windows-latest, 3.12)	1m 38s
Checks / Unit tests / Unit tests (windows-latest, 3.11)	1m 44s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.11)	1m 11s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.14)	1m 4s
Checks / Unit tests / Unit tests (ubuntu-latest, 3.12)	1m 14s
Checks / Actions lint check	33s
Checks / E2E tests (${{ matrix.python-version }}, ${{ matrix.os }})	0s
Checks / Integration tests (${{ matrix.python-version }}, ${{ matrix.os }})	-5s
	15m 52s

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