docs: Add documentation for new Outside Execution utility methods

[VolodymyrBg]

Motivation and Resolution

The documentation for Outside Execution (SNIP-9) was missing information about the new utility methods that were added in version 6.24.0. These methods simplify the process of simulating and estimating fees for outside execution transactions, which is an important feature for developers working with meta-transactions. This PR adds the necessary documentation to ensure users are aware of these new utility methods and understand how to use them effectively.

RPC version (if applicable)

N/A - Documentation update only

Usage related changes

• Added documentation for the new simulateOutsideExecution utility method with example code

• Added documentation for the new estimateFeeOutsideExecution utility method with example code

• Provided explanations about how these utility methods simplify the process of working with outside execution transactions

Development related changes

• Improved documentation completeness by ensuring all features from v6.24.0 are properly documented
• Ensured consistency between CHANGELOG.md and the feature documentation

Checklist:

• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Linked the issues which this PR resolves
• Documented the changes in code (API docs will be generated automatically)
• Updated the tests
• All tests are passing