chore: fix bugs in release workflow

[willarmiros]

Which problem is this PR solving?

• Failed workflow run for 0.15.0

Short description of the changes

This change includes a few fixes/improvements to the publish workflow (which is run automatically after a release PR is merged).

• Actually bootstrap the repo before publishing to avoid compile errors
• Don't regenerate the changelog for the GitHub release entry, instead copy over the entry from the CHANGELOG.md file
• Use lerna publish instead of the publish.sh script

I verified these changes in my test repo here.

My only concern that I can't validate is if there are any permissions/authentication issues with publishing scoped packages via CI, since I've seen that can cause issue: lerna/lerna#2788. @dyladan any concerns on this?

[codecov]

Codecov Report

Merging #417 (ca66f68) into main (1381a9a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #417   +/-   ##
=======================================
  Coverage   94.21%   94.21%           
=======================================
  Files          12       12           
  Lines         432      432           
  Branches       48       48           
=======================================
  Hits          407      407           
  Misses         25       25           

[willarmiros]

Issue that I'm worried about for the auth issues: npm/cli#1637

It says it's fixed by npm login, but I don't know how to perform a login in CI. Unless a username and password secret were added to the repo.

[obecny]

make sure it is merged before releasing the next version of contrib @open-telemetry/javascript-approvers

[obecny]

lgtm