envtest: expose CRDInstallOptions via Environment

[rajathagasthya]

This is related to #481. Currently, there is no way to specify CRDInstallOptions using envtest.Environment, which means you need to workaround like this:

cfg, _ := t.Start()

_, err := envtest.InstallCRDs(cfg, envtest.CRDInstallOptions{
	Paths: []string{
		filepath.Join("..", "..", "..", "test", "integration", "crds"),
	},
	ErrorIfPathMissing: true,
})

But even with this workaround there is no way to control CRD install timeout/interval fields that are part of CRDInstallOptions since they are not exported (hitting an error with CRD install timing out and default timeout is too small):

controller-runtime/pkg/envtest/crd.go

Lines 49 to 53 in 59b131b

	// maxTime is the max time to wait
	maxTime time.Duration
	// pollInterval is the interval to check
	pollInterval time.Duration

So at the very least making those fields exported would be good. Another (better?) solution would be to just include CRDInstallOptions as a field of Environment struct and deprecate CRDs and CRDDirectoryPaths fields since they are already part of CRDInstallOptions struct.

I'm happy to help with a PR if you think this is feasible!