[vectorIntrinsics] RFR: 8261108: Add cast nodes from integer types to float types implementation for Arm SVE [v4]

[Wang Huang]

> Add the backend codegen for nodes like castb2f / castb2d / casts2f / casts2d / casti2f / casti2d / castl2f / castl2d.
> 
> * add `sve_scvtf`  ( and `sve_ucvtf`) encoding
> * add mock for these instructions
> * add `VECTOR_CAST_I2F_EXTEND[N]` and `VECTOR_CAST_I2F`
> 
> Thank you for your review.

Wang Huang has updated the pull request incrementally with one additional commit since the last revision:

  use opc/opc2 instead of T_src/dst

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/37/files
  - new: https://git.openjdk.java.net/panama-vector/pull/37/files/f253db43..ec98d37f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=37&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=37&range=02-03

  Stats: 7 lines in 1 file changed: 3 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/37.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/37/head:pull/37

PR: https://git.openjdk.java.net/panama-vector/pull/37