Core 1.3.2 > 2.0.0 broke ability to use NRF_TIMER_1

This issue was noted when using Khoi Hoang's NRF52_MBED_TimerInterrupt library
[https://github.com/khoih-prog/NRF52_MBED_TimerInterrupt](url)
and was reported here
[https://github.com/khoih-prog/NRF52_MBED_TimerInterrupt/issues/6](url)

It was confirmed by that in Core 1.3.2 NRF_TIMER_1 could be used to trigger an interrupt, but that functionality was broken with the transition to Core 2.0.0.

Can NRF_TIMER_1 availability be brought back?
If not, documentation needs to be changed to indicate that it is not available for timer interrupts.

Start by reviewing the NRF52_MBED_TimerInterrupt library and its linked issue #6, then compare NRF_TIMER_1 interrupt behavior between Core 1.3.2 and Core 2.0.0. Done means restoring NRF_TIMER_1 availability or updating the documentation to state that it cannot be used for timer interrupts.

Written by the indexing model from the issue text.