Update custom view width calculation for TextViews

[CzarMatt]

Overview

Resolved missing horizontal padding when calculating width for custom layouts.

Details

When showing a Balloon with a custom layout, the custom view tree is walked and checked for instances of TextView.

Any TextView widgets, and by extension, descendants of TextView (e.g., Button), has its text measured for calculating width.

The measurement heuristics adds horizontal padding while using compound drawables, but not otherwise. This works great when a custom layout's TextView has no horizontal padding, but constrains text when horizontal padding is present.

Since padding is inside the bounds of the TextView, we would like the resulting maxWidth calculation to contain this extra space information to render the full text.

Here are some example screenshots showing the behavior with and without horizontal padding, before and after this PR's changes:

Before changes with zero horizontal padding

Before changes with 10dp paddingHorizontal

After changes with 10dp paddingHorizontal

---

Reproduction steps

1. Create a new project and surface a Balloon via:

    val balloon = Balloon.Builder(context)
      .setLayout(R.layout.custom_layout)
      .build()
    
    balloon.showAlignBottom(someAnchorView)

where custom_layout is:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="wrap_content">

  <TextView
    android:id="@+id/textview"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:ellipsize="end"
    android:maxLines="1"
    android:paddingHorizontal="20dp"
    android:text="Hello, there!" />

</LinearLayout>

_{Note: can also use padingLeft/paddingStart and paddingRight/paddingEnd to demonstrate the issue.}

Resolution

Add overall horizontal compound padding to TextView's maxWidth measurement always. Also updated the Balloon#measureTextWidth kdoc.

[skydoves]

Looks very good to me! Thank you so much for your contribution 👍