meson: adjust timeouts for some slower tests

meson: adjust timeouts for some slower tests

Adjust the timeouts for the benchmarks (Meson 0.57 allows 0 to mean
infinite) and for the longest running tests.  These are the
times that I measured and the corresponding timeouts.  For generic
qtests, the target that reported the longest runtime is included.

unit tests:
    test-crypto-tlscredsx509        13.15s   45s
    test-crypto-tlssession          14.12s   45s

qtests:
    qos-test                        21.26s   60s   (i386)
    ahci-test                       22.18s   60s
    pxe-test                        26.51s   60s
    boot-serial-test                28.02s   60s   (sparc)
    prom-env-test                   28.86s   60s
    bios-tables-test                50.17s   120s   (aarch64)
    test-hmp                        57.15s   120s   (aarch64)
    npcm7xx_pwm-test                71.27s   150s
    migration-test                  97.09s   150s  (aarch64)
    qom-test                        139.20s  240s  (aarch64)

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>