[cleanup][io] Remove Pulsar IO Twitter connector

[lhotari]

Motivation

The Twitter Firehose API no longer exists and the Pulsar IO Twitter connector has been outdated a long time ago.

Modifications

• Remove Pulsar IO Twitter connector from the Pulsar code base
• Replace usage of Twitter connector in tests with Datagen connector

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Documentation in apache/pulsar-site#1068

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.42%. Comparing base (3efc174) to head (042ee0f).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #25080       +/-   ##
=============================================
+ Coverage     38.49%   74.42%   +35.93%     
- Complexity    13275    34164    +20889     
=============================================
  Files          1864     1917       +53     
  Lines        146403   150462     +4059     
  Branches      17012    17491      +479     
=============================================
+ Hits          56354   111981    +55627     
+ Misses        82341    29552    -52789     
- Partials       7708     8929     +1221     

Flag	Coverage Δ
inttests	26.40% <ø> (+0.01%)	⬆️
systests	22.86% <ø> (+0.09%)	⬆️
unittests	73.96% <ø> (+39.31%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ain/java/org/apache/pulsar/io/core/PushSource.java	100.00% <ø> (+100.00%)	⬆️

... and 1425 files with indirect coverage changes

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