Add less confusing Path constructor
Add less confusing Path constructor

Currently, to construct a directory inside a bucket, you have to make
multiple calls, frequently with multiple empty-string arguments. This is
clearer.
It could alternately replace the existing MakePath entirely, since it should
handle any valid invocation of MakePath identically.

Bug: None
Change-Id: I867dad43283ba5988f8f215b7b784b91dfa93152
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2008476
Auto-Submit: Jacob Kopczynski <ae1854d5a1265c9d01c29a732262ff657a54fa71@chromium.org>
Reviewed-by: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>
Commit-Queue: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go