RFR: 8367324: Avoid redundant parsing when formatting with DigitList [v5]

[Johannes Graham]

> When formatting doubles or BigDecimals, DigitList first formats them as a string and then parses the resultant string to extract the mantissa and the exponent. This can be done more directly. This allows removing some parsing code and removes a cached byte array.
> 
> This also facilitates potential cleanups in FloatingDecimal (removal of getChars method) but I've left that for later to minimize conflicts with other changes there.

Johannes Graham has updated the pull request incrementally with one additional commit since the last revision:

  update assert

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27118/files
  - new: https://git.openjdk.org/jdk/pull/27118/files/e1bbe19d..52bd4eaf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27118&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27118&range=03-04

  Stats: 4 lines in 1 file changed: 2 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/27118.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27118/head:pull/27118

PR: https://git.openjdk.org/jdk/pull/27118