Build against a newer GoLang (#5350)

Build against the newer GoLang 1.22, since the download for 1.15 seems
to have been taken down

<small>By submitting this pull request, I confirm that my contribution
is made under the terms of the [MIT
license](https://github.com/dafny-lang/dafny/blob/master/LICENSE.txt).</small>

.github/workflows/integration-tests-reusable.yml

@@ -91,7 +91,7 @@ jobs:
  - name: Set up oldest supported Go
  uses: actions/setup-go@v5
  with:
- go-version: '1.15'
+ go-version: '1.16'
  cache: false
  - name: Set up goimports
  env:

.github/workflows/runtime-tests.yml

@@ -33,7 +33,7 @@ jobs:
  - name: Set up Go
  uses: actions/setup-go@v5
  with:
- go-version: '1.15'
+ go-version: '1.16'
  cache: false
  - name: Set up goimports
  env:

.github/workflows/standard-libraries.yml

@@ -17,7 +17,7 @@ jobs:
  build:
  needs: check-deep-tests
  if: always() && (( github.event_name == 'pull_request' && (needs.check-deep-tests.result == 'success' || contains(github.event.pull_request.labels.*.name, 'run-deep-tests'))) || ( github.event_name == 'push' && ( github.ref_name == 'master' || vars.TEST_ON_FORK == 'true' )))
- runs-on: macos-latest
+ runs-on: macos-11
 
  steps:
  - name: Checkout Dafny
@@ -32,7 +32,7 @@ jobs:
  - name: Set up Go
  uses: actions/setup-go@v5
  with:
- go-version: '1.15'
+ go-version: '1.16'
  cache: false
  - name: Set up goimports
  env: