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

[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`
 - [ ] Linux x86_64 server fastdebug, `all`

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Commit messages:
 - Leftover
 - Fix

Changes: https://git.openjdk.org/jdk/pull/24250/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24250&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351155
  Stats: 545 lines in 48 files changed: 0 ins; 511 del; 34 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