Add runtime warnings for the deprecated extensions used in Siddhi Apps

[grainier]

Purpose

$title. Currently deprecated = true is only used with doc gen. With this PR it will also give a runtime warning for such extensions.

Samples

@Extension(
        name = "xxxxx",
        deprecated = true,
        namespace = "xxxxx",
        description = "xxxxx",
        examples = {
                @Example(
                        xxxxx
                )
        }
)

Goals

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Approach

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Release note

• deprecated extensions will give a warning at the runtime.

Documentation

n/a

Automation tests

• Unit tests added

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes/no
• Ran FindSecurityBugs plugin and verified report? yes/no
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes/no

Related PRs

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Test environment

n/a