checker: fix: missing check when assignment statement lvalue is ParExpr(fix #19819)

[shove70]

1. Fixed Pointer operations must be wrapped in unsafe #19819
2. Add tests.
3. Fixed related tests.

c := 0
cref := &c

*cref = 1
(*cref) = 1

outputs:

a.v:4:7: error: modifying variables via dereferencing can only be done in `unsafe` blocks
    2 | cref := &c
    3 | 
    4 | *cref = 1
      |       ^
    5 | (*cref) = 1
    6 |
a.v:5:9: error: modifying variables via dereferencing can only be done in `unsafe` blocks
    3 | 
    4 | *cref = 1
    5 | (*cref) = 1
      |         ^
    6 | 
    7 |

[JalonSolov]

Nifty. All 75 V UI examples are failing... but it doesn't say why.

[shove70]

Nifty. All 75 V UI examples are failing... but it doesn't say why.

I guess there are many places where the unsafe block is required

[shove70]

This PR needs to be merged first:
vlang/ui#555

@spytheman , thanks a lot.

[medvednikov]

Great work @shove70 !

I've merged the UI PR.

[shove70]

Great work @shove70 !

I've merged the UI PR.

thanks a lot.