Sandbox LTP genrules

gen_ltp_config used to read files from the source tree,
but this cl refactors it to package all the files it
needs into the tool itself, so it's more hermetic and
all the genrules don't need to explicitly list the files
the tool needs.

go/roboleaf-busy-beavers-sandboxing

Bug: 307824623
Test: diff'd the files produced by the ltp_config_* genrules before/after this change
Change-Id: Ia72084965dcb8659394068b7c6877adb1c882dc2