fix: support T and T? methods with the same name

[i582]

Issue

Closes #1285.

Checklist

• I have updated CHANGELOG.md
• I have added tests to demonstrate the contribution is correctly implemented: this usually includes both positive and negative tests, showing the happy path(s) and featuring intentionally broken cases
• I have run all the tests locally and no test failure was reported
• I have run the linter, formatter and spellchecker
• I did not do unrelated and/or undiscussed refactorings

[anton-trunov]

so, this wouldn't fail at runtime?

contract Foo {
    get fun foo(): Slice {
        let x: map<Int, Int> = emptyMap();
        return x.asCell().asSlice();
    }
}

[Gusarich]

The snippet below throws an internal compiler error.

extends fun foo(self: Int) {
    return self * 2;
}

fun bar(x: Int?) {
    x.foo();
}

[INTERNAL COMPILER ERROR]: Type Int_optional not found
    Please report at https://github.com/tact-lang/tact/issues

       96 |     const msg = `[INTERNAL COMPILER ERROR]: ${message}\nPlease report at https://github.com/tact-lang/tact/issues`;
       97 |     throw source === undefined
    >  98 |         ? new TactInternalCompilerError(msg)
          |           ^
       99 |         : new TactInternalCompilerError(
      100 |               `${locationStr(source)}\n${msg}\n${source.interval.getLineAndColumnMessage()}`,
      101 |               source,

      at throwInternalCompilerError (src/error/errors.ts:98:11)
      at getType (src/types/resolveDescriptors.ts:2113:35)
      at resolveCall (src/types/resolveExpression.ts:644:29)
      at resolveExpression (src/types/resolveExpression.ts:947:20)
      at processStatements (src/types/resolveStatements.ts:434:48)
      at processFunctionBody (src/types/resolveStatements.ts:763:17)
      at resolveStatements (src/types/resolveStatements.ts:803:19)
      at Object.<anonymous> (src/types/resolveStatements.spec.ts:24:36)