fix(linux): load exported CSV and SQL INSERT files back with the same rows

[datlechin]

Summary

• round_trip_suite! in tablepro-test-support, run by every driver (MySQL and MariaDB both, SQLite in the unit suite):
  • value corpus out as CSV, imported into an empty copy, under four writer/reader pairings (every delimiter, quoting always or where needed, LF, CRLF and CR, NULL as NULL). Row count and every row's text compared.
  • corpus out as SQL INSERT, run statement by statement in an editor session against an empty copy. Every value's text and kind compared.
  • a table whose CSV lands within 1 MiB under the 64 MiB limit, imported back and compared row by row. Off on ClickHouse (below).
• MAX_CSV_FILE_BYTES moves from the app to tablepro_core::import so the test reads the same limit.
• Fixed, all found by the new cases:
  • SQLite: a DATE, TIME or DATETIME value with an offset or Z, or in another form SQLite reads, was refused by the import and by cell edits.
  • PostgreSQL: dates and timestamps before year 1 (4713-01-01 BC), from year 10000, or past chrono's last year were refused by the import and by cell edits. One past chrono binds as text cast to the column type.
  • SQL Server: a decimal(38,38) value failed to save or import (tiberius sends precision 39); it now goes as text. Decimal parameters are cast to decimal(38, s), so a multi-row import no longer narrows a full-precision value beside a shorter one.
  • ClickHouse: SQL INSERT export wrote Map and Tuple values as strings the server refuses, and a Variant changed type. They are now JSONExtract('<json>', '<type>').
• Corpus additions: SQLite DATE, TIME and DATETIME forms, PostgreSQL 10000-01-01.
• Docs: linux/docs/testing.md (Export round trip), the PostgreSQL, SQL Server and ClickHouse driver pages, ROADMAP.md.
• No changelog fragment: the Linux app has not shipped.

Not in this PR

• ClickHouse near the import limit: parameters ride in the request URL (64 KiB client cap), so a statement carries 8 KiB of values. 64 MiB is about 8,000 statements at ~67 ms each (async insert wait), about 9 minutes. 128 KiB batches failed with uri too long and Too many form fields. Sending parameters in the body is its own driver change.
• Export defaults: NULL in a text column comes back as '', and formula-like text gets an apostrophe. Both by design; a lossless round trip needs Convert NULL to empty off and the NULL marker.
• Export's Decimal Comma has no import counterpart; a decimal column refuses 1,5 with a clear error.
• A SQLite DATETIME holding a number (Unix time, Julian day) exports as the number, and the import refuses it.
• ClickHouse binds a Tuple from a sorting key as its JSON text in a save's probe, which the server would not parse. Not reproduced.

Test plan

• round_trip_suite! on PostgreSQL, MySQL, MariaDB, SQL Server, ClickHouse (--run-ignored only) and SQLite. Before the fixes the CSV case failed on SQLite, PostgreSQL and SQL Server, and the SQL case on ClickHouse; all pass now.
• SQL Server: csv_import::a_decimal_at_full_precision_keeps_every_digit_beside_shorter_ones, filter::a_decimal_filter_keeps_the_digits_it_was_given.
• Unit tests for eras, far years and SQLite forms in parse_literal_text, PostgreSQL far-date binding, SQL Server decimal encoding and cast, ClickHouse JSON literals.
• Value corpus, CSV import, write batch and filter suites; meson test under xvfb; rustfmt and both clippy runs.

Fixes #3665