Make BitArray.{slice_bits,slice_shots,__getitem__} raise IndexError when indices are not valid (backport #12755)

[mergify]

Summary

This PR updates BitArray.{slice_bits,slice_shots,__getitem__} to raise IndexError if indices are not valid.

Especially, __getitem__ raise IndexError with appropriate message as follows (ba[0, 0, 0] case).

from qiskit.primitives.containers import BitArray

ba = BitArray.from_counts({"0": 2, "1": 3})
ba = ba.reshape(1, 1)

try:
    ba[1]
except Exception as ex:
    print(type(ex), ex)
try:
    ba[0, 0, 0]
except Exception as ex:
    print(type(ex), ex)
try:
    ba[0, 0, 0, 0]
except Exception as ex:
    print(type(ex), ex)

main branch

<class 'IndexError'> index 1 is out of bounds for axis 0 with size 1
<class 'ValueError'> The input array must have at least two axes.
<class 'ValueError'> BitArrays cannot be sliced along the bits axis, see slice_bits() instead.

this PR

<class 'IndexError'> index 1 is out of bounds for axis 0 with size 1
<class 'IndexError'> BitArray cannot be sliced along the shots axis, use slice_shots() instead.
<class 'IndexError'> BitArray cannot be sliced along the bits axis, use slice_bits() instead.

Details and comments

---

This is an automatic backport of pull request #12755 done by [Mergify](https://mergify.com).

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• @Qiskit/terra-core
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[coveralls]

Pull Request Test Coverage Report for Build 10147167107

Details

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• 8 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.002%) to 89.947%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	2	92.11%
crates/qasm2/src/parse.rs	6	96.69%

Totals
Change from base Build 10145758938:	0.002%
Covered Lines:	66200
Relevant Lines:	73599

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💛 - Coveralls