feat: add DROP CONNECTOR functionality

[agavra]

Description

Pretty straightforward, DROP CONNECTOR will now delete a connector.

Testing done

• Unit Tests
• Local Testing

ksql> CREATE SOURCE CONNECTOR `jdbc-connector2` WITH("connector.class"='io.confluent.connect.jdbc.JdbcSourceConnector',"connection.url"='jdbc:postgresql://localhost:5432/almog.gavra',"mode"='bulk',"topic.prefix"='jdbc2-', "key"='username');

 Message
-----------------------------------
 Created connector jdbc-connector2
-----------------------------------
ksql> DROP CONNECTOR "jdbc-connector2";

 Message
-------------------------------------
 Dropped connector "jdbc-connector2"
-------------------------------------

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[hjafarpour]

LGTM.
Why do we have different headers for the result of create and drop? For create it's Message and for drop it is Success.

[hjafarpour]

Should we also have (IF EXISTS) here?

[agavra]

I don't feel strongly about this, but using an IF EXISTS will require an extra call to connect. If it doesn't exist you just get a 404 in the response, which is probably okay.

[agavra]

Why do we have different headers for the result of create and drop? For create it's Message and for drop it is Success.

huh I thought I changed this! Must've not updated the PR. My intention was to have Message

EDIT: I changed this in the code but not in my testing done example 😂