Reduce LoadedApkAssets LRU cache size.

The cached apk assets can take up multiple megabytes of .apk mmap and
native memory for associated data structures. Reduce the cache size
for potential multi-megabyte memory savings with hopefully no
noticeable performance impacts.

In particular, rough estimates of the memory and performance impacts
of this change were evaluated by starting the launcher app,
sampling system server PSS with dumpsys meminfo and cache stats using
dumpsys activity for a few different cache sizes:

LRU Size   1: cached apks: total= 1 created=0 evicted=33 hit= 0 miss=34 max=1    TOTAL PSS=187542
LRU Size   3: cached apks: total= 3 created=0 evicted=12 hit=19 miss=15 max=3    TOTAL PSS=190606
LRU Size  15: cached apks: total=15 created=0 evicted= 0 hit=19 miss=15 max=15   TOTAL PSS=199350
LRU Size 100: cached apks: total=15 created=0 evicted= 0 hit=19 miss=15 max=100  TOTAL PSS=201416

Comparing cache stats after launching the settings app:

LRU Size   3: cached apks: total=3 created=0 evicted=5 hit=14 miss=8 max=3
LRU Size  15: cached apks: total=6 created=0 evicted=0 hit=18 miss=6 max=15

Running performance tests locally to ensure no clear regression in app
startup:

app-startup/benchmark-app-hermetic/cold-dropcache-test:
LRU                15        3        3
activityStart:    40.47    38.53    39.27
bindApplication:  24.40    24.53    24.93
draw:              4.27     4.33     4.07
layout:            0.73     1.07     0.73
onCreate:          9.40     9.00     8.53
totalLaunchTime: 183.13   183.27   187.07

app-startup/hermetic-apps/cold-dropcache-test:

LRU                   15       15          3         3
Calculator_avg:      333.9    333.1      343.3      334.6
Calculator_max:      345.0    360.0      370.0      363.0
Calculator_median:   333.5    331.5      343.5      333.5
Calculator_min:      320.0    317.0      320.0      311.0
Calculator_std_dev:    6.62    13.26      18.22      16.51
Clock_avg:           510.0    511.2      509.2      512.6
Clock_max:           529.0    528.0      530.0      529.0
Clock_median:        510.5    509.0      503.5      512.0
Clock_min:           498.0    495.0      487.0      492.0
Clock_std_dev:         7.70    11.71      15.25      11.07
Contacts_avg:        457.7    527.3      507.3      543.9
Contacts_max:        602.0    622.0      591.0      588.0
Contacts_median:     410.5    568.5      568.0      580.0
Contacts_min:        390.0    374.0      366.0      394.0
Contacts_std_dev:     85.64    96.80      88.80      72.97
Phone_avg:          6073.1    6109.7    6110.8     6115.8
Phone_max:          6196.0    6208.0    6180.0     6222.0
Phone_median:       6070.0    6117.5    6100.0     6133.5
Phone_min:          5982.0    5990.0    6061.0     5994.0
Phone_std_dev:        61.49     67.35     34.55      60.17
Settings_avg:        457.9     446.6     451.6      428.7
Settings_max:        487.0     468.0     494.0      449.0
Settings_median:     460.0     450.0     444.5      424.0
Settings_min:        423.0     421.0     431.0      420.0
Settings_std_dev:     21.21     12.02     20.46       9.71

Bug: 79115008
Test: Device boots.
Test: dumpsys activity all shows ResourcesManager max cache size of 3.

Change-Id: I7225b6978fac6197c27bec23d2b477fb1f5aee43