Implement devfile support

[sspeiche]

Implement devfile support per agreed upon implementation plan #2290

This is needed to support new model for inner loop (hot redeploy) touch points and further work on supporting specific runtimes.

[kadel]

The first stage will be just consuming devfiles (odo push).
A detailed description will be in #2470

[rajivnathan]

/area devfile

[jichenjc]

@kadel could you please help to show where we can find when the devfile will be in release ? I was told odo-init-image will be replaced by this devfile feature, can I know when it might happen? Thanks

[openshift-bot]

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/lifecycle stale

[girishramnani]

/lifecycle frozen

[girishramnani]

This issue is quite huge as we can observe the https://github.com/openshift/odo/issues?q=is%3Aopen+is%3Aissue+label%3Aarea%2Fdevfile
but currently features that are essential to have feature parity that are left are https://github.com/openshift/odo/issues?q=is%3Aopen+is%3Aissue+label%3Arequired-for-v2+label%3Aarea%2Fdevfile

Now mostly all of them have people assigned to them (except 1) and many have PRs as well. so this epic will be done for 2.0 milestone.

[girishramnani]

the feature parity so far is attained and we have another epic #3782 for follow up for devfile support.
Closing this issue as the AC is achieved.