RFR: 8283013: Simplify Arguments::parse_argument() [v2]

[Ioi Lam]

> - Remove all the complex `sscanf()` calls in `Arguments::parse_argument()`
> - Call the appropriate parsing function according to the type of the flag
> - Added more test cases for flags of the `double` type.
> 
> As a result of this change, `double` flags can now be specified in more ways, as long as the input is accepted by `strtod()`. However, `NaN` and `INFINITY` values are not allowed because the VM probably cannot handle them. Please see the test case for details.
> 
> Tested with tiers 1-5.

Ioi Lam has updated the pull request incrementally with two additional commits since the last revision:

 - Disabled test for CompileThresholdScaling due to JDK-8283807
 - @dholmes-ora comments

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7916/files
  - new: https://git.openjdk.java.net/jdk/pull/7916/files/8413d876..0faa4cca

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7916&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7916&range=00-01

  Stats: 10 lines in 2 files changed: 4 ins; 3 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7916.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7916/head:pull/7916

PR: https://git.openjdk.java.net/jdk/pull/7916