Initial commit for new 1.6 release with Postgres 13 support. (#1257)

* Initial commit for new 1.6 release with Postgres 13 support.
* Updating maintainers, Go version, Codeowners.
* Use lazy upgrade image that contains pg13.
* fix typo for ownerReference
* fix clusterrole in helm chart
* reflect GCP logical backup in validation
* improve PostgresTeam docs
* change defaults for enable_pgversion_env_var and storage_resize_mode
* explain manual part of in-place upgrade
* remove gsoc docs

Co-authored-by: Felix Kunde <felix-kunde@gmx.de>

.github/workflows/run_e2e.yaml

@@ -14,7 +14,7 @@ jobs:
     - uses: actions/checkout@v1
     - uses: actions/setup-go@v2
       with:
-          go-version: "^1.15.5"
+          go-version: "^1.15.6"
     - name: Make dependencies
       run: make deps mocks
     - name: Compile

.github/workflows/run_tests.yaml

@@ -14,7 +14,7 @@ jobs:
     - uses: actions/checkout@v1
     - uses: actions/setup-go@v2
       with:
-          go-version: "^1.15.5"
+          go-version: "^1.15.6"
     - name: Make dependencies
       run: make deps mocks
     - name: Compile