[EAGLE-1068] Upgrade Siddhi dependency to v5.1.4

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## Purpose
Purpose of this pull request is to upgrade the [Siddhi](https://mvnrepository.com/artifact/io.siddhi) dependency version to `v5.1.4`. With this, it'll also;
- Fix `alert-core` and tests to support new Siddhi APIs.
- Fix existing custom Siddhi extensions to support new Siddhi APIs.
- Improve extension loading (use annotation support instead of `siddhiext`).
- Add the following dependencies (since they are now separated from Siddhi core);


## Remarks
- Fixes https://issues.apache.org/jira/browse/EAGLE-1068
- https://issues.apache.org/jira/browse/EAGLE-1065

Contribution Tasks:
 - [x] Make sure the PR title is formatted like:
   `[EAGLE-<Jira issue #>] Description of pull request`
 - [x] Make sure tests pass via `mvn clean verify`. (Even better, enable
       Travis-CI on your fork and ensure the whole test matrix passes).
 - [x] Replace `<Jira issue #>` in the title with the actual Jira issue
       number, if there is one.
 - [ ] If this contribution is large, please file an Apache
       [Individual Contributor License Agreement](https://www.apache.org/licenses/icla.txt).


Author: Grainier <grainier@wso2.com>

Closes #1003 from grainier/EAGLE-1068.
44 files changed