RFR: 8292758: put support for UNSIGNED5 format into its own header file [v5]

[Coleen Phillimore]

On Wed, 7 Sep 2022 01:05:38 GMT, John R Rose <jrose at openjdk.org> wrote:

>> Refactor code from inside of CompressedStream into its own unit.
>> 
>> This code is likely to be used in future refactorings, such as JDK-8292818 (replace 96-bit representation for field metadata with variable-sized streams).
>> 
>> Add gtests.
>
> John R Rose has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add missing "this->"

src/hotspot/share/utilities/unsigned5.hpp line 190:

> 188:   // reports the largest uint32_t value that can be encoded using len bytes
> 189:   // len must be in the range [1..5]
> 190:   static constexpr uint32_t max_encoded_in_length(uint32_t len) {

A few of the classes make the gtest test a friend so that internal functions can be private.

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PR: https://git.openjdk.org/jdk/pull/10067