Motivation:

`HttpConversionUtil.toHttp2Headers` currently depends on `java.net.URI`
for absolute-form request-target parsing. On JDKs that still enforce
older URI syntax, path or query characters that appear in real HTTP
request-targets can make HTTP/1.x to HTTP/2 conversion fail before
`:path` is produced.

Netty only needs URI parsing for the lower-frequency
`scheme://authority` validation/extraction path. The hot path/query
extraction can follow the same lightweight parsing shape used by Vert.x
while avoiding full URI parsing and avoiding a try/catch fallback.

Modification:

- Split request-target path and query parsing into Vert.x-shaped
`parsePath` and `parseQuery` helpers, with comments for Netty-specific
differences.
- Keep `URI` parsing for `scheme://authority` validation/extraction only
after stripping path/query/fragment data.
- Preserve origin-form and asterisk-form behavior.
- Add regression tests for characters rejected by `java.net.URI`,
authority-only and missing-authority absolute-form targets, empty
query/fragment handling, and malformed authority validation.
- Add a Jazzer fuzz test that compares the new behavior against the old
URI-based conversion using broad `consumeString(128)` request-target
input and narrow documented compatibility exceptions.

Result:

HTTP/2 conversion no longer relies on full `java.net.URI` parsing for
request-target path/query extraction, while preserving meaningful
existing behavior and continuing to validate/extract scheme and
authority through URI where appropriate.

Verification performed locally:

- `./mvnw -pl codec-http2 -Drevapi.skip=true -DskipJapicmp
-DskipHttp2Testsuite -DskipAutobahn test`
- `JAZZER_FUZZ=1 ./mvnw -pl codec-http2 -Drevapi.skip=true -DskipJapicmp
-DskipHttp2Testsuite -DskipAutobahn -Dcheckstyle.skip=true
-Dtest=HttpConversionUtilFuzzTest test`
- `./mvnw -pl codec-http2 -Drevapi.skip=true -DskipJapicmp
-DskipHttp2Testsuite -DskipAutobahn -Dcheckstyle.skip=true
-Dsurefire.failIfNoSpecifiedTests=false
-Dtest=HttpConversionUtilTest,HttpConversionUtilFuzzTest test`

---------

Co-authored-by: multicode <multicode@yawk.at>
(cherry picked from commit a42c7fc)