Fix remaining uninitialized variable and field Coverity defects

[bryancall]

Problem

Coverity reported several uninitialized variable and field defects in core HTTP/TLS code and experimental plugins, which could lead to undefined behavior and non-deterministic runtime state.

Changes

• Initialize core proxy structs -- add in-class brace defaults for HttpVCTableEntry and HostStatRec fields so entries and host state begin in a deterministic state.
• Initialize protocol parsing fields -- default ChunkedHandler::max_chunk_size and TLSSNISupport::ClientHello::_ext_len to known values.
• Initialize plugin locals -- set explicit initial values for cache_fill parsing enum and txn_box feature return state.
• Address portability in constructor init -- remove memset from HttpVCTable construction and rely on proper initialization, avoiding non-portable treatment of pointer-to-member-function types.

Testing

• CI passed on GitHub checks
• Verify Coverity marks CIDs 1021690, 1508845, 1533658, 1534712, 1544456, and 1645800 as fixed on next analysis run

[Copilot]

Pull request overview

This PR addresses a set of Coverity “uninitialized variable / field” defects by adding deterministic default initialization for several structs and locals across core proxy code and experimental plugins.

Changes:

• Add in-class member initialization for HttpVCTableEntry, HostStatRec, ChunkedHandler::max_chunk_size, and TLSSNISupport::ClientHello::_ext_len.
• Initialize previously uninitialized locals in experimental plugins (txn_box Feature return value, cache_fill enum op).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
plugins/experimental/txn_box/plugin/src/Ex_Base.cc	Initialize Feature return value to NIL_FEATURE to avoid default/uninitialized state.
plugins/experimental/cache_fill/configs.cc	Initialize Content-Length comparison operator enum before parsing.
include/proxy/http/HttpVCTable.h	Add in-class initialization for all HttpVCTableEntry members.
include/proxy/http/HttpTunnel.h	Default-initialize ChunkedHandler::max_chunk_size.
include/proxy/HostStatus.h	Default-initialize HostStatRec fields to a known state.
include/iocore/net/TLSSNISupport.h	Default-initialize ClientHello::_ext_len to 0.

[bneradt]

Pretty sraightforward.