RFR: JDK-8319307: DCmds should not assert on truncation and should report truncation [v2]

[Thomas Stuefe]

> `bufferedStream` was originally intended to provide intermediate output buffering; the buffer was supposed to drain upon flushing. However, in many cases, `flush()` is a no-op, so the buffer never gets drained.
> 
> To prevent infinitely raising buffer sizes for non-flushing `bufferedStream`, [JDK-8220394](https://bugs.openjdk.org/browse/JDK-8220394) introduced the notion of a "maximum reasonable cap". Upon reaching this threshold, we assert in debug VMs since we assumed this to be a condition worth analyzing. In release VMs, we silently truncate.
> 
> But DCmds - one of the primary users of `bufferedStream` - can reach the maximum cap under normal conditions; one example would be printing the list of dynamic libraries on Linux (just prints the process memory map) - this can get very large. Similarly, NMT detail reports and VM.info output can get just as large.
> 
> Therefore, neither asserting nor silent truncation is optimal. Instead, we should truncate the output, print a visible truncation marker, and - if possible - interrupt the printing.
> 
> ---
> 
> The patch is minimally invasive to simplify review. Like most stream classes, `bufferedStream` would benefit from an overhaul, but I'd like to leave that to a future RFE.
> 
> Testing: Tested manually with a number of commands with artificially increased output size. GHAs (Windows test errors unrelated).

Thomas Stuefe has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8319307-DCmds-should-not-assert-on-truncation-and-should-report-truncation
 - fix mac builds
 - JDK-8319307-DCmds-should-not-assert-on-truncation-and-should-report-truncation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16474/files
  - new: https://git.openjdk.org/jdk/pull/16474/files/996deab9..51a005ac

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16474&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16474&range=00-01

  Stats: 7830 lines in 195 files changed: 2815 ins; 2471 del; 2544 mod
  Patch: https://git.openjdk.org/jdk/pull/16474.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16474/head:pull/16474

PR: https://git.openjdk.org/jdk/pull/16474