fix(dirtyRect): text dirty rect considered when text in host

[linghaoSu]

• Resolve useDirtyRect = true and saving image shows "Save as Image" label apache/echarts#16534

Why

when enabling dirty rect, and then clicking the button in the toolbox, the zrender consider where should to repainted, but does not consider text when they are hosted in another element, so, maybe we should consider ignore textElment when they hosted in other element and the host element that is ignored.

Before

After

[pissang]

We can treat __hostTarget as a special parent and doing both check in the

zrender/src/graphic/Displayable.ts

Line 229 in 458d111

let parent = this.parent;

if (considerAncestors) {
      let node = this;
      while (node) {
          if (node.ignore) {
              return false;
          }
          node = node.parent || node.__hostTarget;
      }
  }

[linghaoSu]

Wow, I agree with this way, we don't need to modify the api of shouldBePainted, I have fixed this using these codes. Please review again.

[linghaoSu]

hi, @pissang Is there anything else wrong with this pr