[Impeller] Make IsEmpty methods on Rect and Size NaN-aware

[flar]

Removes unused or redundant overloads and fixes the IsEmpty method on Size to be both simpler (2 comparisons vs. 4) and NaN-aware. Rect automatically uses the new code via delegation to the Size object.

[flar]

Specific tests are added to test the IsEmpty methods. A couple of other files were using redundant overloaded methods that I deleted for simplicity, and while I could not find any direct unit tests for those methods, they are likely tested by any rendering code. One of the files is used for image decompression and should be covered by any image decompression tests.

The test cases were added first and showed the following failures before updating the methods:

Failures before the fix

Note: Google Test filter = *IsEmpty*
[==========] Running 4 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 4 tests from SizeTest
[ RUN      ] SizeTest.RectIsEmpty
../../flutter/impeller/geometry/rect_unittests.cc:77: Failure
Value of: Rect::MakeXYWH(1.5, 2.3, 10.5, nan).IsEmpty()
  Actual: false
Expected: true
../../flutter/impeller/geometry/rect_unittests.cc:78: Failure
Value of: Rect::MakeXYWH(1.5, 2.3, nan, 7.2).IsEmpty()
  Actual: false
Expected: true
../../flutter/impeller/geometry/rect_unittests.cc:79: Failure
Value of: Rect::MakeXYWH(1.5, 2.3, nan, nan).IsEmpty()
  Actual: false
Expected: true
[  FAILED  ] SizeTest.RectIsEmpty (0 ms)
[ RUN      ] SizeTest.IRectIsEmpty
[       OK ] SizeTest.IRectIsEmpty (0 ms)
[ RUN      ] SizeTest.SizeIsEmpty
../../flutter/impeller/geometry/size_unittests.cc:31: Failure
Value of: Size(10.5, nan).IsEmpty()
  Actual: false
Expected: true
../../flutter/impeller/geometry/size_unittests.cc:32: Failure
Value of: Size(nan, 7.2).IsEmpty()
  Actual: false
Expected: true
../../flutter/impeller/geometry/size_unittests.cc:33: Failure
Value of: Size(nan, nan).IsEmpty()
  Actual: false
Expected: true
[  FAILED  ] SizeTest.SizeIsEmpty (0 ms)
[ RUN      ] SizeTest.ISizeIsEmpty
[       OK ] SizeTest.ISizeIsEmpty (0 ms)
[----------] 4 tests from SizeTest (0 ms total)

[----------] Global test environment tear-down
[==========] 4 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 2 tests.
[  FAILED  ] 2 tests, listed below:
[  FAILED  ] SizeTest.RectIsEmpty
[  FAILED  ] SizeTest.SizeIsEmpty

Results after the fix

Note: Google Test filter = *IsEmpty*
[==========] Running 4 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 4 tests from SizeTest
[ RUN      ] SizeTest.RectIsEmpty
[       OK ] SizeTest.RectIsEmpty (0 ms)
[ RUN      ] SizeTest.IRectIsEmpty
[       OK ] SizeTest.IRectIsEmpty (0 ms)
[ RUN      ] SizeTest.SizeIsEmpty
[       OK ] SizeTest.SizeIsEmpty (0 ms)
[ RUN      ] SizeTest.ISizeIsEmpty
[       OK ] SizeTest.ISizeIsEmpty (0 ms)
[----------] 4 tests from SizeTest (0 ms total)

[----------] Global test environment tear-down
[==========] 4 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 4 tests.