Merge main into the MLT branch

main moved each tool's option table to file scope so that usage.cpp can
generate the usage message from it (#409), which conflicted with the
tables the MLT options had been added to. The three MLT options move to
the file-scope tables, under the same headings they were listed with
before: "Setting or disabling tile size limits" in tippecanoe and
tile-join, and "Output tile" in tippecanoe-overzoom.

Also combine the new radix-sort-test with the MLT tests in the test
target, add usage.o to the tools that gained MLT objects, keep both the
MLT=0 and the new docs CI jobs, and regenerate the man page for the
README changes, which the docs job now checks.

.gitignore

@@ -38,6 +38,9 @@ tippecanoe-json-tool
 tippecanoe-overzoom
 unit
 
+# Left behind if man page generation fails
+man/tippecanoe.1.tmp
+
 # Tests
 tests/**/*.mbtiles
 tests/**/*.check