fix ignoring chain operator for member function call · Pull Request !928 · OpenHarmony-SIG/arkcompiler_ets_frontend

# Brief
This PR is to fix issue with not processing chain operator while accessing class member functions: [[ArkTS frontend] Unhandled NullPointerException by using ?.](https://gitee.com/openharmony-sig/arkcompiler_ets_frontend/issues/I87CWY?from=project-issue)

Change-Id: Id66c029ef4da18e693925e1442e2281e5f0357bf

## Problem analysis
While working on the issue we've found two following issues:
1. while parsing the '?.' operator the parser successfully detects it and creates object of the "member expression" class, but then on the next loop iteration the parser detects the function  call itself and handles it as regular one whiteout being informed that it is the optional operator (may be we should process call expression in-place? see open question 1);
2. while generating the byte code the `optional_` variable isn't count for member access expressions;

## Problem solution
So in order to fix the original issue it is required to track detected chain operator and have the `ParsePostPrimaryExpression()` invoked with properly set flag for that. Also it is required to add Null-ptr branch checking generation while generating code for accessing class member function.

## Changed files:
- parser/ETSparser.cpp: the function `ParsePostPrimaryExpression()` is updated with respect to track the detected chain operator for subsequent call to `ParseCallExpression()` in order to let it construct the `CallExpression` object properly;
- ir/expressions/callExpression.cpp: the function `CallExpression::Compile()` is updated with respect to the value of the `optional_` class variable, to put null-ptr check for member function call while generating byte-code;
- test/parser/ets/optional_chaining_nested_property-expected.txt: updated with respect to AST data.

## Open questions
1. May be we should process call expression in-place, just for those branch when the chain operator is detected and processed? Since so far, it seems to the [specific code for that branch, which calls to `ParseCallExpression()`](https://gitee.com/openharmony-sig/arkcompiler_ets_frontend/blob/master/parser/ETSparser.cpp#L3724) isn't invoked et all;

## Testing
The testing is done by following:
1. the original sample from the issue is compiled and run without errors;
2. the `ninja ets_tests` command status: pass, no issues;
3. the `ninja tests_full` command status: pass, no issues;

类型	指派人员	状态
审查	klooer Anton Soldatov ragnvald public_ARKCIAccount Dmitrii Trubenkov Ishin Pavel	进行中 (0/1人)
测试	public_ARKCIAccount	进行中 (0/1人)

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