RFR: 8286401: Address possibly lossy conversions in Microbenchmarks [v2]

[Claes Redestad]

> #8599 would add a new warning. This address the conversions in the microbenchmark component by means of making the types precise or adding explicit casts. There's quite a few changes in the ByteBuffers benchmarks, but the real change is in the template as these are generated.
> 
> I've run through a subset of the affected benchmarks and verified that the results are either neutral or improve somewhat (seem to be the case in a few of the ByteBuffer micros).

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Copyrights, consistently use the exact accumulator type

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8654/files
  - new: https://git.openjdk.java.net/jdk/pull/8654/files/5cba7820..41f37a25

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8654&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8654&range=00-01

  Stats: 17 lines in 11 files changed: 0 ins; 0 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8654.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8654/head:pull/8654

PR: https://git.openjdk.java.net/jdk/pull/8654