Global Key manager feature back end changes

[prasa7]

This PR adds the global Key manager feature(Cross tenant API invocation)

[CLAassistant]

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1 out of 2 committers have signed the CLA.

:white_check_mark: prasa7
:x: Prasanna Dangalla

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[codecov[bot]]

Codecov Report

Attention: 255 lines in your changes are missing coverage. Please review.

Comparison is base (13b6312) 41.76% compared to head (230e797) 41.86%.

Files	Patch %	Lines
...pimgt/rest/api/admin/v1/dto/PaginationApisDTO.java	0.00%	54 Missing :warning:
...admin/v1/impl/GlobalKeyManagersApiServiceImpl.java	3.84%	50 Missing :warning:
...bon/apimgt/rest/api/admin/v1/dto/ApiResultDTO.java	0.00%	46 Missing :warning:
...mgt/rest/api/admin/v1/dto/SearchResultListDTO.java	0.00%	38 Missing :warning:
...java/org/wso2/carbon/apimgt/impl/APIAdminImpl.java	15.78%	13 Missing and 3 partials :warning:
...o2/carbon/apimgt/impl/AMDefaultKeyManagerImpl.java	71.73%	9 Missing and 4 partials :warning:
...2/carbon/apimgt/impl/factory/KeyManagerHolder.java	65.62%	4 Missing and 7 partials :warning:
...a/org/wso2/carbon/apimgt/impl/APIConsumerImpl.java	0.00%	6 Missing :warning:
...apimgt/rest/api/admin/v1/GlobalKeyManagersApi.java	28.57%	5 Missing :warning:
...on/apimgt/rest/api/admin/v1/dto/KeyManagerDTO.java	44.44%	5 Missing :warning:
... and 4 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #12262 +/- ## ============================================ + Coverage 41.76% 41.86% +0.09% - Complexity 3220 3240 +20 ============================================ Files 1824 1830 +6 Lines 134600 134920 +320 Branches 19447 19484 +37 ============================================ + Hits 56220 56480 +260 - Misses 71617 71641 +24 - Partials 6763 6799 +36 ``` | [Flag](https://app.codecov.io/gh/wso2/carbon-apimgt/pull/12262/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2) | Coverage Δ | | |---|---|---| | [integration_tests](https://app.codecov.io/gh/wso2/carbon-apimgt/pull/12262/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2) | `35.13% <27.76%> (+0.14%)` | :arrow_up: | | [unit_tests](https://app.codecov.io/gh/wso2/carbon-apimgt/pull/12262/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2) | `20.60% <1.63%> (-0.05%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wso2#carryforward-flags-in-the-pull-request-comment) to find out more.

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[npamudika]

Public fixes for https://github.com/wso2/api-manager/issues/2017