chore: add type annotations to vmware imc config_file

[anujsingh-cse]

Proposed Commit Message

chore: add type annotations to vmware imc config_file

Removing cloudinit.sources.helpers.vmware.imc.config_file and
tests.unittests.sources.vmware.test_vmware_config_file from the mypy
override list in pyproject.toml surfaces six errors.

config_file.py: the standard configparser idiom
config.optionxform = str assigns a class to a method, which mypy flags
as both method-assign and assignment; this is intentional (disables
option lowercasing) and follows the existing ignore style used in
cloudinit/config/schema.py.

test_vmware_config_file.py: two assertions chain .get("nameservers").get(...)
which mypy sees as union-attr because dict.get returns Optional. Adding
the {} default keeps runtime behavior identical when the key is present
and makes the Optional case explicit.

Refs GH-5445

Additional Context

Refs GH-5445. Claimed in #5445 (comment).

Removing both modules from the override list surfaces six errors:

config_file.py:61: error: Cannot assign to a method  [method-assign]
config_file.py:61: error: Incompatible types in assignment
                (expression has type "type[str]",
                 variable has type "Callable[[str], str]")  [assignment]
test_vmware_config_file.py:164: error: Item "None" of "Any | None"
                has no attribute "get"  [union-attr]
test_vmware_config_file.py:165: error: ... [union-attr]
test_vmware_config_file.py:188: error: ... [union-attr]
test_vmware_config_file.py:189: error: ... [union-attr]

• config.optionxform = str is the documented configparser pattern for
  preserving key case; mypy cannot express "assign the builtin str as
  the transform function" against the bound-method type, so it is
  ignored with the same comment style already used at
  cloudinit/config/schema.py:523.
• The four test errors are .get("nameservers").get(...) chains where
  the first .get is Optional. Supplying {} as the default makes
  the chain total; when the key is present (as in every fixture used
  here) behavior is unchanged.

No signatures change, so there is no effect on callers.

Test Steps

$ python -m mypy cloudinit/ tests/ tools/
(with override entries removed; the two target files report 0 errors)

$ pytest tests/unittests/sources/vmware/test_vmware_config_file.py -q
22 passed in 1.25s

$ ruff check (target files)
All checks passed!

tox -e py3 and tox -e check_format to be confirmed by CI (developed
on Windows where the full tox suite cannot run).

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[holmanb]

Thanks, one comment.

[holmanb]

Please include a comment documenting why this is needed.

[anujsingh-cse]

Added a comment above the line explaining why the ignore is needed (the documented configparser idiom for preserving key case, which mypy cannot express against a method type) — 0a37e72.

[anujsingh-cse]

Rebased onto current main to clear the conflict with #7107 (both PRs edited the same mypy override list region). The pyproject resolution keeps both removals, and the shadowing/Optional test commit dropped from this branch since #7107 already carried the identical content upstream — the module now type-checks and passes against the merged state, as intended.

Also carrying one lint fix so check_format is green on the fresh run: #6958 introduced two ISC004 (implicit string concatenation) errors in test_azure_helper.py on main, which every merge-ref CI run currently inherits; the two concatenations are parenthesized with no value change.

Verified locally: ruff check . (pinned 0.16.2) passes on the whole tree, mypy is clean for config_file and the vmware test module, and all 22 vmware config-file tests pass.