RFR: 8355572: Support HTTP Range requests in Simple Web Server [v4]

[Peyang]

> Hi all,
> 
> [JEP 408](https://openjdk.org/jeps/408) introduced the Simple Web Server in Java 18, providing a minimal webserver for serving static files over HTTP.
> 
> [RFC 9110](https://www.rfc-editor.org/rfc/rfc9110.html#name-range-requests) defines "Range Requests" as an optional feature that allows clients to request a subset of a resource's content. Supporting Range requests in the context of JDK's Simple Web Server means enabling the server to serve only the requested portion of a static file.
> 
> This change contains:
> 
> 1. Enhances `sun.net.httpserver.simpleserver.FileServerHandler` in the `jdk.httpserver` module to support `Range` and `If-Range` headers.
> 2. Calculates an `ETag` for each resource based on its last-modified date and file size and sends it to the client on demand for use with the `If-Range` header.
> 3. Returns the `Accept-Ranges` header for all file retrievals, and `Content-Range` when a client requests a specific range.
> 4. Adds a new constant `HTTP_RANGE_NOT_SATISFIABLE` to the `Codes` class to indicate invalid ranges.
> 5. Returns `206 Partial Content` for valid ranges and `416 Range Not Satisfiable` for invalid ranges.
> 6. Includes corresponding tests to verify correct behavior.
> 
> This enhancement was motivated by recent discussions on the net-dev mailing list, which requested support for Range requests along with example use cases: https://mail.openjdk.org/pipermail/net-dev/2025-April/026364.html
> It was also discussed briefly on the net-dev mailing list: https://mail.openjdk.org/pipermail/net-dev/2025-October/028586.html

Peyang has updated the pull request incrementally with four additional commits since the last revision:

 - Enhance HTTP Range header support by making parseRangeHeader() public and adding comprehensive tests for valid and invalid range headers
 - Remove redundant import statements
 - Add quick explanation of parseRangeHeader() method
 - Fix number formatting to use string interpolation instead of %d to avoid locale issues

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28021/files
  - new: https://git.openjdk.org/jdk/pull/28021/files/96486d34..0b979c74

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28021&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28021&range=02-03

  Stats: 93 lines in 4 files changed: 86 ins; 2 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/28021.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28021/head:pull/28021

PR: https://git.openjdk.org/jdk/pull/28021