[cmdlineargs] Limit total number of threads in oversubscription test

[staticfloat]

This test was exhausting our limit of 1000 PIDs because the machine it
was running on has 128 cores, which ends up trying to launch a Julia
process with 1280 threads.

[Keno]

Fixes #38631 (hopefully).

[vtjnash]

Win32 failure is interesting (and unrelated)

macOS failure looks like a problem with Artifacts / pkg server

[vtjnash]

This still might be too many for 32-bit machines, as this is 1.6 GB of stacks:

$ /data/vtjnash/julia/build-x86/usr/bin/julia -t 200 -e 'print(Threads.nthreads())'
OpenBLAS blas_thread_init: pthread_create failed for thread 1 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max
OpenBLAS blas_thread_init: pthread_create failed for thread 2 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max
OpenBLAS blas_thread_init: pthread_create failed for thread 3 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max
OpenBLAS blas_thread_init: pthread_create failed for thread 4 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max
OpenBLAS blas_thread_init: pthread_create failed for thread 5 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max
OpenBLAS blas_thread_init: pthread_create failed for thread 6 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max
OpenBLAS blas_thread_init: pthread_create failed for thread 7 of 8: Resource temporarily unavailable
OpenBLAS blas_thread_init: RLIMIT_NPROC 1542271 current, 1542271 max

signal (11): Segmentation fault
in expression starting at none:0
unknown function (ip: (nil))
Allocations: 2649 (Pool: 2644; Big: 5); GC: 0
Segmentation fault

$ /data/vtjnash/julia/build-x86/usr/bin/julia -t 200 -e 'print(Threads.nthreads())'
WARNING: Error during initialization of module LinearAlgebra:
ErrorException("could not load library "libopenblas"
libopenblas.so: failed to map segment from shared object")
fatal: error thrown and no exception handler available.
InitError(mod=:Profile, error=ErrorException("could not allocate space for 10000000 instruction pointers"))
unknown function (ip: 0xe533e49d)
unknown function (ip: 0xe533e354)
unknown function (ip: 0xe533e136)
unknown function (ip: 0xe533e154)
jl_apply_generic at /data/vtjnash/julia/build-x86/usr/bin/../lib/libjulia-internal.so.1.7 (unknown line)
unknown function (ip: 0xf7a208c3)
unknown function (ip: 0xf7a06e34)
julia_init__threading at /data/vtjnash/julia/build-x86/usr/bin/../lib/libjulia-internal.so.1.7 (unknown line)
repl_entrypoint at /data/vtjnash/julia/build-x86/usr/bin/../lib/libjulia-internal.so.1.7 (unknown line)
main at /data/vtjnash/julia/cli/loader_exe.c:51
__libc_start_main at /lib/i386-linux-gnu/libc.so.6 (unknown line)
_start at /data/vtjnash/julia/build-x86/usr/bin/julia (unknown line)