[PR #6741/568814fc backport][stable-7] New module: pnpm package manager (#7225)

New module: pnpm package manager (#6741)

* (feat) New module pnpm added

A new module for pnpm is added. Necessary entries were written to
BOTMETA.yml.

* (feat) Basic tests added

* (feat) reduced nesting of ifs

* (fix) trying to fix up CI pipelines

* (fix) incorrect indentation of alias fixed

* (feat) fixed further indentations

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

* (fix) various linting and CI errors fixed/ignored

* (feat) reduced restriction, new install method

Some restrictions on OS are reduced. New installation method, similar to
the official installation method, is provided.

* (fix) ignoring CentOS 6 for CI.

* retrigger checks

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit 568814fc3e)

Co-authored-by: Aritra Sen <125266845+aretrosen@users.noreply.github.com>

tests/integration/targets/pnpm/templates/package.j2

@@ -0,0 +1,13 @@
+{#
+Copyright (c) Ansible Project
+GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+SPDX-License-Identifier: GPL-3.0-or-later
+#}
+{
+  "name": "ansible-pnpm-testing",
+  "version": "1.0.0",
+  "license": "MIT",
+  "dependencies": {
+    "reading-time": "^1.5.0"
+  }
+}