RFR: 8351155: C1/C2: Remove 32-bit x86 specific FP rounding support [v2]

[Aleksey Shipilev]

> C1 and C2 have support for rounding double/floats, to support awkward rounding modes of x87 FPU. With 32-bit x86 port removed, we can remove those parts. This basically deletes all the code that uses `strict_fp_requires_explicit_rounding`, which is now universally `false` for all supported platforms.
> 
> For C1, we remove `RoundFP` op, its associated `lir_roundfp` and related utility methods that insert these nodes in the graph.
> 
> For C2, we remove `RoundDouble` and `RoundFloat` nodes (note there is a confusingly named `RoundDoubleMode` nodes that are not related to this), associated utility methods, AD match rules that reference these nodes (as nops!), and some `Ideal`-s that are no longer needed.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `tier1`
>  - [x] Linux x86_64 server fastdebug, `all`

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Minor leftover

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24250/files
  - new: https://git.openjdk.org/jdk/pull/24250/files/376c5ad8..88e4589c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24250&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24250&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24250.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24250/head:pull/24250

PR: https://git.openjdk.org/jdk/pull/24250