Various add-ons still use the deprecated `undodb` module

[gareth-rees]

The undodb Automation API module was deprecated in UDB version 8.0. The relevant changelog entry is:

Renamed the `undodb` Python package, part of the UDB Automation API (see
https://docs.undo.io/AutomationAPI.html), to `undo`. Importing `undodb`
is still supported, but it will cause a warning to be emitted and will
be removed in a future release. [#28263]

However, several add-ons continue to use the deprecated module name:

$ grep -RI undodb\\. .
./_linters/mypy.ini:[mypy-undodb.debugger_extensions]
./_linters/mypy.ini:[mypy-undodb.udb_launcher]
./sample_functions/sample_functions.py:from undodb.debugger_extensions import (
./regs_every_bb/regs_every_bb.py:from undodb.debugger_extensions import (
./count_calls/count_calls.py:from undodb.udb_launcher import (
./count_calls/count_calls_extension.py:from undodb.debugger_extensions import udb
./reconstruct_file/reconstruct_file.py:from undodb.debugger_extensions import debugger_io, debugger_utils, udb
./backtrace_with_time/backtrace_with_time.py:from undodb.debugger_extensions import (