Refactor action execution request data model

[Shenali-SJ]

Description

This PR updateds the action execution component by refactoring the data types of the additionalHeaders and additionalParams fields in the action request object to align with the API contract.

Updated request object:

{
    "additionalHeaders": [
        {
            "name": "accept",
            "value": [
                "application/json"
            ]
        },
        {
            "name": "cache-control",
            "value": [
                "no-cache"
            ]
        }
    ],
    "additionalParams": [
        {
            "name": "TestParam",
            "value": [
                "test"
            ]
        }
    ],
    "clientId": "r***************************a",
    "grantType": "client_credentials",
    "scopes": [
        "test_scope_1",
        "test_scope_2"
    ]
}

Related Issue:

• Pre-issue-access-token-action request is not compatible with the provided API contract product-is#21305

Related PRs:

• Refactor pre issue access token action request object wso2-extensions/identity-inbound-auth-oauth#2590

Followup Actions:

• Merge Refactor pre issue access token action request object wso2-extensions/identity-inbound-auth-oauth#2590

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 40.10%. Comparing base (9715437) to head (d5218fd).
Report is 19 commits behind head on master.

Files with missing lines	Patch %	Lines
...arbon/identity/action/execution/model/Request.java	0.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6022      +/-   ##
============================================
- Coverage     40.17%   40.10%   -0.07%     
- Complexity    14172    14179       +7     
============================================
  Files          1734     1736       +2     
  Lines        116863   117262     +399     
  Branches      20081    20153      +72     
============================================
+ Hits          46953    47033      +80     
- Misses        62694    62991     +297     
- Partials       7216     7238      +22     

Flag	Coverage Δ
unit	23.94% <83.33%> (+0.01%)	⬆️

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