RFR: 8257147: [TESTBUG] Set a larger default loop count for the VectorAPI jtreg tests [v2]

[Xiaohong Gong]

> The current default loop count of VectorAPI tests is too small (10 for load/store tests, 100 for arithmetic tests) to make the tests compiled with C2. This makes some potential issues not be reported as expected.
> 
> This patch fixes it by setting a larger default iteration.
> 
> The whole tests running time increases with this patch. Here is the results on two different types of machines:
> 
> Running with "`-conc:10`":
>              Before     After
> System A     5m30s      6m43s
> System B     5m1s       6m31s
> 
> Running with "`-conc:1`":
>              Before     After
> System A     26m52s     45m6s
> System B     30m3s      43m30s

Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:

  Close tiered compilation for each test without changing the loop count

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1621/files
  - new: https://git.openjdk.java.net/jdk/pull/1621/files/56bca764..8bb9bacf

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1621&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1621&range=00-01

  Stats: 158 lines in 64 files changed: 0 ins; 0 del; 158 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1621.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1621/head:pull/1621

PR: https://git.openjdk.java.net/jdk/pull/1621