ACME: new helper module for ACME challenges which need TLS certs (#43756)

* Added helper module for generating ACME challenge certificates.

* Soft-fail on missing cryptography. Also check version.

* Adding integration test.

* Move acme_challenge_cert_helper from web_infrastructure to crypto/acme.

* Adjusting to draft-05.

* The cryptography branch has already been merged.

test/integration/targets/acme_challenge_cert_helper/aliases

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+shippable/cloud/group1
+cloud/acme

test/integration/targets/acme_challenge_cert_helper/meta/main.yml

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+dependencies:
+  - setup_acme

test/integration/targets/acme_challenge_cert_helper/tasks/main.yml

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+---
+- block:
+  - name: Create ECC256 account key
+    command: openssl ecparam -name prime256v1 -genkey -out {{ output_dir }}/account-ec256.pem
+  - name: Obtain cert 1
+    include_tasks: obtain-cert.yml
+    vars:
+      select_crypto_backend: auto
+      certgen_title: Certificate 1
+      certificate_name: cert-1
+      key_type: rsa
+      rsa_bits: 2048
+      subject_alt_name: "DNS:example.com"
+      subject_alt_name_critical: no
+      account_key: account-ec256
+      challenge: tls-alpn-01
+      challenge_alpn_tls: acme_challenge_cert_helper
+      modify_account: yes
+      deactivate_authzs: no
+      force: no
+      remaining_days: 10
+      terms_agreed: yes
+      account_email: "example@example.org"
+
+  when: openssl_version.stdout is version('1.0.0', '>=') or cryptography_version.stdout is version('1.5', '>=')

test/integration/targets/acme_challenge_cert_helper/tasks/obtain-cert.yml

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+../../setup_acme/tasks/obtain-cert.yml