[Monorepo] - Step 1 - import golang repos

[eapolinario]

Describe your changes

This PR is the first step in the consolidation of the Flyte components into a monorepo.

In this PR we only imported the code for the golang components. Each component was moved to a top-level directory with its commits history intact.

In order to preserve the commit history we import each of the components in a two-step process:

1. Prepare the component repo to be imported.
   i. we do this by rewriting the commit history of each component's master branch at a particular git sha.
   ii. we move each file to a directory named the same as the component (so as to decrease the chances of a collision)
   iii. for example, compare the commits between the current master branch in flyteadmin with the prepared version in https://github.com/flyteorg/flyteadmin/tree/prepare-for-monorepo.
2. Import the branch in the flyte repo by allowing unrelated histories to be merged.
   i. Being very specific, run git merge --allow-unrelated-histories $COMPONENT/prepare-for-monorepo, assuming that $COMPONENT is a remote added to the flyte repo.

This table describes what the original git SHA was used while importing the component:

component	git sha
datacatalog	flyteorg/datacatalog@b5a958f
flyteadmin	flyteorg/flyteadmin@6f49854
flytecopilot	flyteorg/flytecopilot@5a38c21
flyteplugins	flyteorg/flyteplugins@552f145
flytepropeller	flyteorg/flytepropeller@476d416
flytestdlib	flyteorg/flytestdlib@4b950ec