Optimize ECPoint serialization

[shargon]

Description

Avoid BinaryWritter on ECPoint like with UIntXXX

Type of change

• Optimization (the change is only an optimization)
• Style (the change is only a code style for better maintenance or standard purpose)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Current

Test Configuration:

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[cschuchardt88]

Please fix

Error: /home/runner/work/neo/neo/tests/Neo.UnitTests/TestUtils.cs(46,40): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.UnitTests/Neo.UnitTests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.UnitTests/SmartContract/UT_KeyBuilder.cs(94,29): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.UnitTests/Neo.UnitTests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.UnitTests/SmartContract/UT_KeyBuilder.cs(107,29): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.UnitTests/Neo.UnitTests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.Plugins.OracleService.Tests/TestUtils.cs(36,40): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.Plugins.OracleService.Tests/Neo.Plugins.OracleService.Tests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.UnitTests/TestUtils.cs(46,40): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.UnitTests/Neo.UnitTests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.UnitTests/SmartContract/UT_KeyBuilder.cs(94,29): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.UnitTests/Neo.UnitTests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.UnitTests/SmartContract/UT_KeyBuilder.cs([107](https://github.com/neo-project/neo/actions/runs/13315568797/job/37188684692?pr=3757#step:4:108),29): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.UnitTests/Neo.UnitTests.csproj]
Error: /home/runner/work/neo/neo/tests/Neo.Plugins.OracleService.Tests/TestUtils.cs(36,40): error CS1503: Argument 1: cannot convert from 'Neo.IO.ISerializable' to 'byte' [/home/runner/work/neo/neo/tests/Neo.Plugins.OracleService.Tests/Neo.Plugins.OracleService.Tests.csproj]