Better type handling to account for types-docutils bump

[amoghrajesh]

types-docutils released types-docutils 0.21.0.20250715 with more stricter checks for types under nodes.

Adding some reactive type checks in our devel common modules to account / address that.

Example failure: https://github.com/apache/airflow/actions/runs/16287041685/job/45988572938

Error:

devel-common/src/sphinx_exts/substitution_extensions.py:64: error: Unsupported right operand type for in ("Node")  [operator]
                if _SUBSTITUTION_OPTION_NAME not in node:
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
devel-common/src/sphinx_exts/substitution_extensions.py:79: error: "Node" has no attribute "replace"  [attr-defined]
                        child = nodes.Text(child.replace(f"|{name}|", replacement))
                                           ^~~~~~~~~~~~~
devel-common/src/sphinx_exts/substitution_extensions.py:80: error: "Node" has no attribute "replace"  [attr-defined]
                    node.replace(old_child, child)
                    ^~~~~~~~~~~~
devel-common/src/sphinx_exts/substitution_extensions.py:83: error: "Node" has no attribute "rawsource"; maybe "source"?  [attr-defined]
                node.rawsource = node.astext()
                ^~~~~~~~~~~~~~
Found 4 errors in 1 file (checked 84 source files)

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[amoghrajesh]

Failing tests are unrelated

[Dev-iL]

Heh you beat me to it with this PR.

BTW, is the fact that a new types-docutils that breaks builds was merged requires some CI-reconfiguration so as not to happen again?