Move ISSUE_TEMPLATE (#1567)

This PR moves the `ISSUE_TEMPLATE` to the root and removes the old ones.

polkadot/.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,13 +0,0 @@
----
-name: Bug report
-about: Create a report to help us improve
-title: ''
-labels: ''
-assignees: ''
-
----
-
-- It would help if you submit info about the system you are running, e.g.: operating system, kernel version, amount of available memory and swap, etc.
-- Logs could be very helpful. If possible, submit the whole log. Please format it as ```code blocks```.
-- Describe the role your node plays, e.g. validator, full node or light client.
-- Any command-line options were passed?

polkadot/.github/ISSUE_TEMPLATE/release.md

@@ -1,52 +0,0 @@
----
-name: Release issue template
-about: Tracking issue for new releases
-title: Polkadot {{ env.VERSION }} Release checklist
----
-# Release Checklist
-
-This is the release checklist for Polkadot {{ env.VERSION }}. **All** following
-checks should be completed before publishing a new release of the
-Polkadot/Kusama/Westend/Rococo runtime or client. The current release candidate can be
-checked out with `git checkout release-{{ env.VERSION }}`
-
-### Runtime Releases
-
-These checks should be performed on the codebase prior to forking to a release-
-candidate branch.
-
-- [ ] Verify [`spec_version`](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#spec-version) has been incremented since the
-    last release for any native runtimes from any existing use on public
-    (non-private) networks. If the runtime was published (release or pre-release), either
-    the `spec_version` or `impl` must be bumped.
-- [ ] Verify previously [completed migrations](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#old-migrations-removed) are
-    removed for any public (non-private/test) networks.
-- [ ] Verify pallet and [extrinsic ordering](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#extrinsic-ordering) has stayed
-    the same. Bump `transaction_version` if not.
-- [ ] Verify new extrinsics have been correctly whitelisted/blacklisted for
-    [proxy filters](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#proxy-filtering).
-- [ ] Verify [benchmarks](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#benchmarks) have been updated for any modified
-    runtime logic.
-
-The following checks can be performed after we have forked off to the release-
-candidate branch or started an additional release candidate branch (rc-2, rc-3, etc)
-
-- [ ] Verify [new migrations](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#new-migrations) complete successfully, and the
-    runtime state is correctly updated for any public (non-private/test)
-    networks.
-- [ ] Verify [Polkadot JS API](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#polkadot-js) are up to date with the latest
-    runtime changes.
-- [ ] Check with the Signer's team to make sure metadata update QR are lined up
-- [ ] Push runtime upgrade to Westend and verify network stability.
-
-### All Releases
-
-- [ ] Check that the new client versions have [run on the network](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#burn-in)
-    without issue for 12+ hours on >75% of our validator nodes.
-- [ ] Check that a draft release has been created at
-    https://github.com/paritytech/polkadot/releases with relevant [release
-    notes](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#release-notes)
-- [ ] Check that [build artifacts](https://github.com/paritytech/polkadot/blob/master/doc/release-checklist.md#build-artifacts) have been added to the
-    draft-release
-- [ ] Check that all items listed in the [milestone](https://github.com/paritytech/polkadot/milestones) are included in the release.
-- [ ] Ensure that no `freenotes` were added into the release branch after the latest generated RC