gh-107932: Fix dis module for bytecode that does not have an associated source line

[CorvinM]

Fix dis module for bytecode that does not have an associated source line.
fixes #107932

This does change behavior of many of the dis.py public functions to display lines with no source line mapping as such.
At the very least it changes:
findlinestarts - now returns starts of bytecode blocks that dont have a source line with lineno=None
dis/disassemble/distb/disco - now separates and labels lineno=None bytecode blocks, previously it lumped them into the previous block (see #107932)
get_instructions & Instruction - Instruction objects now have starts_line=False to indicate that the instruction does not start a line.

• Issue: dis.dis() reports line numbers where there are none. #107932

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[markshannon]

Thanks for working on this.
The changes look correct, but the use of False as a special value for starts_line is a bit hard to follow.

Lib/test/test_dis.py is an endless source of merge conflicts, so I'll try merge ASAP after you've made the changes.

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[CorvinM]

@markshannon Thanks for the quick review! I have made the requested changes; please review again. I have also updated the docs to reflect the changes and resolved the merge conflict (for now). I've listed the changes in the docs as happening in 3.13 (is this the correct procedure for the project?)

[bedevere-bot]

Thanks for making the requested changes!

@markshannon: please review the changes made to this pull request.

[markshannon]

Thanks, looks good.

[erlend-aasland]

main has been broken since this was merged.

[markshannon]

#108478