[yaml2obj] Migrate to OptTable (#224964)
yaml2obj is one of three tools that parse with
cl::ParseCommandLineOptions(LongOptionsUseDoubleDash=true). Parse its
options with an OptTable instead, so that the mode can be removed from
cl::. Spellings follow the other migrated tools: -D<macro>=<v> and
-D <macro>=<v>, -o<file> and -o <file>, --docnum=<n> and --docnum <n>,
--max-size likewise, -E, -h/--help and --version. `-o=<file>` is no
longer accepted; the tests that used it are updated. `--help` lists
only yaml2obj's options.
LLM-aided
