easy options string storage

[icing]

easy option string storage

Change the storage of easy handle option strings from an array sized for
all possible options to a hash set to reduce memory footprint.

Give the hash set initially room for 4 strings, with first allocation
happening when it goes beyond that. Measurements with our test suite
and a forced fail on growing the set gives:

Size Result
2 ---> 1261 tests out of 1951 reported OK: 64%
4 ---> 1792 tests out of 1951 reported OK: 91%
8 ---> 1944 tests out of 1951 reported OK: 99%
16 ---> 1949 tests out of 1951 reported OK: 99%
32 ---> single fail of 3211, unit test for u8_strset

Add u8_strset that keeps the tuples (uint8_t id, char *str)
and allows set/unset by id. Add that as data->set.strings.

Define MACROS

• CURL_EASY_STR(data, id) for access
• CURL_EASY_STR_SET(data, id, s) for setting, making a copy
• CURL_EASY_STR_SETN(data, id, s) for setting, no copy
• CURL_EASY_STR_CLEAR(data, id) for unsetting
• CURL_EASY_STR_CLEAR0(data, id) for unsetting and zero-ing value

Add data->set.str_copypostfields to handle former STRING_COPYPOSTFIELDS
string that was not always a string and could carry NUL bytes.

Add unit tests to test3211.

[Copilot]

Pull request overview

Replaces the easy handle’s fixed string array with a compact uint8_t-keyed hash set.

Changes:

• Adds Robin Hood hash-set storage and access macros.
• Migrates option handling and consumers to the new storage.
• Separates binary COPYPOSTFIELDS storage and adds unit coverage.

Reviewed changes

Copilot reviewed 44 out of 44 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/unit/unit3211.c	Tests the new string set.
tests/unit/unit1620.c	Updates string cleanup assertions.
tests/data/test3211	Updates test description.
lib/vtls/wolfssl.c	Migrates wolfSSL string access.
lib/vtls/vtls.c	Migrates ECH access.
lib/vtls/vtls_config.c	Migrates TLS configuration strings.
lib/vtls/schannel.c	Migrates pinned-key access.
lib/vtls/rustls.c	Migrates ECH strings.
lib/vtls/openssl.c	Migrates OpenSSL option strings.
lib/vtls/mbedtls.c	Migrates pinned-key access.
lib/vtls/gtls.c	Migrates pinned-key access.
lib/vssh/vssh.c	Migrates SSH key options.
lib/vssh/libssh2.c	Migrates libssh2 options.
lib/vssh/libssh.c	Migrates libssh options.
lib/vquic/vquic.c	Migrates QUIC ECH access.
lib/vquic/vquic-tls.c	Migrates QUIC TLS options.
lib/vquic/cf-quiche.c	Migrates custom request access.
lib/vquic/cf-ngtcp2.c	Migrates custom request access.
lib/vdns/doh.c	Migrates DoH configuration strings.
lib/vdns/asyn-ares.c	Migrates resolver options.
lib/urldata.h	Defines hash-set storage and macros.
lib/url.c	Initializes, clears, and reads the set.
lib/uint-hashset.h	Declares the string hash set.
lib/uint-hashset.c	Implements the string hash set.
lib/transfer.c	Migrates transfer URL handling.
lib/smtp.c	Migrates SMTP option strings.
lib/setopt.h	Updates the string setter API.
lib/setopt.c	Migrates option storage and post fields.
lib/rtsp.c	Migrates RTSP option strings.
lib/proxy.c	Migrates proxy option strings.
lib/pop3.c	Migrates custom request access.
lib/Makefile.inc	Adds hash-set sources.
lib/imap.c	Migrates custom request access.
lib/http2.c	Migrates HTTP/2 request access.
lib/http.c	Migrates HTTP option strings.
lib/http_proxy.c	Migrates proxy user-agent access.
lib/http_httpsig.c	Migrates HTTP signature options.
lib/http_aws_sigv4.c	Migrates AWS signature options.
lib/getinfo.c	Migrates returned option strings.
lib/ftp.c	Migrates FTP option strings.
lib/easy.c	Duplicates hash-set and post-field storage.
lib/cookie.c	Migrates cookie-jar access.
lib/cf-socket.c	Migrates bind options.
lib/cf-haproxy.c	Migrates HAProxy client IP access.

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[bagder]

This PR shrinks the Curl_easy struct by almost 600 bytes...