Rename 'unittests' to 'gles-unittest'

Now that we have vk-unittests, it makes sense to prefix unittests by their API name.

Fixes a couple of TODOs

Change-Id: I57234d6b19c3dd4f130b211a0be4e604613b8cd8
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28399
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
diff --git a/.travis.yml b/.travis.yml
index 815c05f..a4a5d5c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,7 +22,7 @@
   - mkdir -p build && cd build
   - cmake -DREACTOR_BACKEND=$REACTOR_BACKEND ..
   - make -j2
-  - ./unittests
+  - ./gles-unittests
   - ./ReactorUnitTests
 
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