Unit checking
This is the main PR of MCP-0027.
Opening as Draft pull request, reflecting the current MCP status being In Development.
A long discussion foregoing this PR can be found in #2127.
@HansOlsson, @casella how do you feel about rebranding MCP-0027 as Unit checking in order to avoid abandoning this MCP just to open up another one with broader scope?
I wonder if it's worth carrying all the history of this MCP. We could close this and keep it for the record. Maybe a a fresh start with a new one would be better?
I believe it makes sense to rebrand MCP-0027 as Unit checking; instead of "Units of Literal Constants". I understand the concern by @casella - but to me it suffices to start a new PR if needed, and having all of the unit-issues and pull requests with the same label MCP-0027 label will make it easier to keep track of everything we have found out so far.