Revert "[VM] Remove unused flags"

This reverts commit 1a4cff1bd42002ab7289aa73594634a7cc242fab.

Reason for revert: The precompiled arm bot failed a test.

Original change's description:
> [VM] Remove unused flags
> 
> Remove the following flags which are always ON
> --strong
> --reify_generic_functions
> 
> and these flags which are not applicable anymore
> --error-on-bad-override
> --error-on-bad-type
> --enable-type-checks
> 
> Change-Id: I6e1aeb68e663953f4ae49ca94ea0daa87b661900
> Reviewed-on: https://dart-review.googlesource.com/c/79431
> Commit-Queue: Siva Annamalai <asiva@google.com>
> Reviewed-by: Alexander Markov <alexmarkov@google.com>
> Reviewed-by: Régis Crelier <regis@google.com>

TBR=rmacnak@google.com,alexmarkov@google.com,asiva@google.com,regis@google.com

Change-Id: Ib0fe4f33c044047ef1cb31bca9d38591176b7d40
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/84883
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Siva Annamalai <asiva@google.com>