RFR: 8255305: Add Linux x86_32 tier1 to submit workflow [v2]

[Aleksey Shipilev]

> Following JDK-8254282, it seems useful to also run tier1 tests on 32-bit platform, because that finds problems with runtime tests and internal asserts. Those problems do not show up during the plain build. Again, while x86_32 might not be widely deployed by itself, but 32/64 bit cleanliness detects bugs that manifest on ARM32 early.
> 
> I did most of the work to fix all current regressions in x86_32 tier1, the only exception is JDK-8255331, which is supposed to be fixed by #833

Aleksey Shipilev has updated the pull request incrementally with four additional commits since the last revision:

 - Rename "x32" -> "x86" in the test steps
 - Merge branch 'JDK-8255412-add-x32-default' into JDK-8255305-32bit-tier1
 - Rename x32 -> x86.
 - 8255412: Add "Linux x32" to platform selection default in custom submit workflow

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/830/files
  - new: https://git.openjdk.java.net/jdk/pull/830/files/d8e687a9..ff6ca97d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=830&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=830&range=00-01

  Stats: 29 lines in 1 file changed: 0 ins; 0 del; 29 mod
  Patch: https://git.openjdk.java.net/jdk/pull/830.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/830/head:pull/830

PR: https://git.openjdk.java.net/jdk/pull/830