RFR: 8356709: Avoid redundant String formatting in BigDecimal.valueOf(double) [v4]

[Johannes Graham]

> Optimize `BigDecimal.valueOf(double)` by using `FormattedFPDecimal` instead of converting to decimal string and then parsing it. This results in an approximate 6x improvement for me.

Johannes Graham has updated the pull request incrementally with three additional commits since the last revision:

 - Update src/java.base/share/classes/jdk/internal/math/FormattedFPDecimal.java
   
   Align better with spec
   
   Co-authored-by: Raffaello Giulietti <raffaello.giulietti at oracle.com>
 - Update src/java.base/share/classes/jdk/internal/math/FormattedFPDecimal.java
   
   Better alignment with spec
   
   Co-authored-by: Raffaello Giulietti <raffaello.giulietti at oracle.com>
 - Update src/java.base/share/classes/jdk/internal/math/FormattedFPDecimal.java
   
   Add another final
   
   Co-authored-by: Raffaello Giulietti <raffaello.giulietti at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25173/files
  - new: https://git.openjdk.org/jdk/pull/25173/files/e7d2d14b..0cc32fc0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25173&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25173&range=02-03

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/25173.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25173/head:pull/25173

PR: https://git.openjdk.org/jdk/pull/25173