new-install fails on packages with tests/benchmarks unless --disable-tests/benchmarks is used

[fgaz]

For example, cabal new-install pandoc fails this assertion:

cabal/cabal-install/Distribution/Client/ProjectPlanning.hs

Lines 241 to 245 in 52a7d51

	-- either a package is built inplace, or we are not attempting to
	-- build any test suites or benchmarks (we never build these
	-- for remote packages!)
	. assert (elabBuildStyle == BuildInplaceOnly ||
	Set.null elabStanzasAvailable)

This is easily fixed by setting the tests and benchmarks as disabled in every ElaboratedConfiguredPackage (or at an earlier stage) in CmdInstall.hs.