Update the Manual Per-Platform Testing section in the Releasing a New Version of DynamoRIO page.

**Describe the bug**
The Manual Per-Platform Testing section needs to be updated. Some of the steps are not up to date, for example:
- samples/bin64/libbbsize.so has been moved to api/bin/libbbsize.so
- bin64/drrun -t drltrace/drmemory results in unknown 64-bit tool error.
- for cmake -DDynamoRIO_DIR=$PWD/../cmake/ ../samples, samples is now under api, i.e. ../api/samples
- sub-directory drmemory is not found.