Add a notification to publish artifacts to the client

[nipunayf]

Purpose

The PR defines a new notification allowing the LS to send notifications to the client upon project updates. Additionally, this resolves concurrency issues in the event pub-sub handler.

Fixes wso2/product-ballerina-integrator#88

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 75.07%. Comparing base (f3b07a4) to head (16a7da8).
Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
...ng/langserver/eventsync/EventSyncPubSubHolder.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #43962      +/-   ##
============================================
+ Coverage     75.05%   75.07%   +0.01%     
- Complexity    57512    57525      +13     
============================================
  Files          3540     3540              
  Lines        222373   222403      +30     
  Branches      28835    28840       +5     
============================================
+ Hits         166908   166961      +53     
+ Misses        46201    46173      -28     
- Partials       9264     9269       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.