constants: Rename QR_OP_*, add QR_VIA_RAPI

Commit 28b71a76 added a list of resources which can be queried using
LUXI. Unfortunately the variable was named “QR_OP_LUXI”, which can be
confusing. This patch renames “QR_OP_QUERY” to “QR_VIA_OP”, “QR_OP_LUXI”
to “QR_VIA_LUXI” and adds a new variable, currently equal to
“QR_VIA_LUXI”, for remote API queries (mostly for documentation).

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>