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).

[mergify]

Cherry-pick of bfd2eea has failed:

On branch mergify/bp/stable/1.1/pr-12755
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  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	new file:   releasenotes/notes/fix-bitarray-slice-bits-shots-c9cb7e5d907722f5.yaml
	modified:   test/python/primitives/containers/test_bit_array.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   qiskit/primitives/containers/bit_array.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[qiskit-bot]

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• @Qiskit/terra-core
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[coveralls]

Pull Request Test Coverage Report for Build 10147304891

Details

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• 10 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.009%) to 89.953%

---

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	4	92.11%
crates/qasm2/src/parse.rs	6	97.61%

Totals
Change from base Build 10110765446:	0.009%
Covered Lines:	61860
Relevant Lines:	68769

---

💛 - Coveralls