ci: markdown linting cleanups

[blumamir]

This PR includes the following fixes:

• apply Lint changelog file CI step to all markdowns and not only the one in the repo root. This introduced few fixes to existing CHANGELOG files which now failed to lint
• exclude all CHANGELOG.md files from the next ci step Lint markdown files, which makes it consistent with contrib
• align all our markdowns to common style - dash for unordered lists in markdown.
• added rule to CI to enforce the list marker style
• cleanup irrelevant paths from the "ignroe" option in the ci step config for markdown-lint. they refer to times when the exporters where part of the packages directory and not under experimental.

see #4698 and the equivalent contrib PR: https://github.com/open-telemetry/opentelemetry-js-contrib/pull/2205