Tune timeout for test targets (go/attt-lsc).

[//session:session_test]: We're adjusting the test target timeout because it has a 0.302572 percent time out rate based on last week's (2024-08-17 - 2024-08-24) tap postsubmit running statistics. Its original timeout_sec is 60, and we're adjusting it to moderate, which is 300 seconds.
Some detailed statistics for the target (before this CL):
  Num of invocation: 5350
  Num of passed invocations: 5272
  Num of timeout invocations: 16
  ****** Stats for passing runs ******
    Min run time in secs: 0
    Max run time in secs: 201
    Mean run time in secs: 11.090288
    Sd run time in secs: 18.355576

[//session:session_converter_stress_test]: We're adjusting the test target timeout because it has a 0.302629 percent time out rate based on last week's (2024-08-17 - 2024-08-24) tap postsubmit running statistics. Its original timeout_sec is 300, and we're adjusting it to long, which is 900 seconds.
Some detailed statistics for the target (before this CL):
  Num of invocation: 5350
  Num of passed invocations: 5271
  Num of timeout invocations: 16
  ****** Stats for passing runs ******
    Min run time in secs: 0
    Max run time in secs: 334
    Mean run time in secs: 7.009486
    Sd run time in secs: 17.786684

Tested:
    Local presubmit tests passed.
PiperOrigin-RevId: 667932374

src/session/BUILD.bazel

@@ -122,7 +122,7 @@ mozc_cc_test(
 mozc_cc_test(
  name = "session_converter_stress_test",
  size = "small",
- timeout = "moderate",
+ timeout = "long",
  srcs = ["session_converter_stress_test.cc"],
  shard_count = 8,
  deps = [
@@ -180,6 +180,7 @@ mozc_cc_library(
 mozc_cc_test(
  name = "session_test",
  size = "small",
+ timeout = "moderate",
  srcs = ["session_test.cc"],
  shard_count = 8,
  deps = [