shared: util.c: unify split and split_quoted
strv: multiple cleanups

- turn strv_merge into strv_extend_strv.
   appending strv b to the end of strv a instead of creating a new strv
- strv_append: remove in favor of strv_extend and strv_push.
- strv_remove: write slightly more elegant
- strv_remove_prefix: remove unused function
- strv_overlap: use strv_contains
- strv_printf: STRV_FOREACH handles NULL correctly
Remove unused variables
shared/install: use char** convention for strvs
journal: Add missing byte order conversions

Convert entry_array.items[0] to host byte order prior to passing it to
chain_cache_put().

[zj: also use le64toh in journal-verify.c]

https://bugs.freedesktop.org/show_bug.cgi?id=73194