docs(filters): present-tense 5.0 filter changes

[soyuka]

Summary

The 5.0 filter docs still spoke about main (5.0) in the future tense and never documented what
actually shipped in api-platform/core#8351 (d37a75379). This PR aligns core/filters.md,
core/doctrine-filters.md, and core/jsonapi.md with the shipped code.

• ComparisonFilter [between] is real: documented as a first-class operator with a worked example
  and its generated SQL, replacing the "In 4.4 there is no dedicated between operator" / "in 5.0 it
  also gains…" future-tense language. Also fixed a stale "five OpenAPI parameters" count (now six,
  between included).
• RangeFilter is deprecated since 4.4, removed in 6.0 (not 5.0) — added a proper [!WARNING]
  deprecation callout on the ## Range Filter section itself and synced the core/filters.md list
  entry, which only said "legacy" before.
• DateFilter and ExistsFilter no longer extend AbstractFilter (standalone classes as of 5.0).
  Documented this as an internal rewrite only — URL syntax and behavior are unchanged; it only
  matters for anyone who subclassed those filters directly.
• PropertyAwareFilterInterface::getProperties() is now a real interface method (previously a
  commented-out // TODO: 5.x uncomment method). Updated the custom-filter example under "Decorate
  a Doctrine filter using Symfony" so SearchTextAndDateFilter actually implements the interface
  with both setProperties()/getProperties(), and explained what getProperties() returns.
• core/jsonapi.md: use_iri_as_id already defaults to false on main (5.0) —
  Configuration.php:103-104 (booleanNode('use_iri_as_id')->defaultFalse()). Rewrote the "will
  become the default in 5.x" line to describe the current default and pointed to
  core/upgrade-guide.md for the migration (kept minimal — another agent owns that section).
• core/filters.md: enable_link_security was removed from Configuration.php entirely in 5.0
  (feat!: remove deprecated APIs scheduled for 5.0 core#8367 — the 4.4 deprecation said "always enabled and will be removed in API
  Platform 5.0"). Replaced the "enable it first" instructions for ReadLinkParameterProvider with a
  one-line note, matching the phrasing used for the same change in docs: remove config keys deleted in 5.0, document %param% resolution #2334
  (core/subresources.md).

Verified against source (core upstream/main @ d37a75379, PR #8351)

• ComparisonFilter::OPERATOR_BETWEEN = 'between' — both
  src/Doctrine/Orm/Filter/ComparisonFilter.php and the ODM equivalent.
• Value separator is a literal .. (explode('..', $value, 2)), both bounds must be is_numeric
  (coerced to int/float) — [between] does not accept DateTime bounds, only combining
  gte/lte does.
• ORM: ExactFilter::apply() emits sprintf('%1$s.%2$s BETWEEN :%3$s_1 AND :%3$s_2', ...) when
  $context['operator'] === ComparisonFilter::OPERATOR_BETWEEN, or collapses to = when both
  bounds are equal.
• ODM: no native BETWEEN; ComparisonFilter::applyBetween() expands to a gte/lte pair instead.
• RangeFilter docblock: @deprecated since API Platform 4.4: ... This filter is removed in 6.0
  (both ORM and ODM RangeFilter.php).
• DateFilter/ExistsFilter class declarations changed from extends AbstractFilter (4.4) to
  standalone final class ... implements FilterInterface, ..., PropertyAwareFilterInterface (main).
• PropertyAwareFilterInterface::getProperties(): ?array is a real abstract method on main.
• Configuration.php:103 — ->booleanNode('use_iri_as_id')->defaultFalse().
• git grep -n enable_link_security upstream/main -- src/ returns nothing (only a hit on
  upstream/4.4, where it's still present but deprecated).

A note on commit 1 and pre-existing Prettier drift

core/doctrine-filters.md and core/filters.md came into main via #2316 already Prettier-dirty
(npx prettier@3.9.5 --check fails on upstream/main for these two files before this PR). Since
Prettier reformats the whole file rather than just touched hunks, commit 1
(docs(filters): present-tense 5.0 filter changes) unavoidably carries that pre-existing reflow
alongside the content changes — there wasn't a safe way to isolate a prettier-only commit ahead of
it without a history rewrite, which I avoided. The repo-wide prettier --check passes clean as of
this PR's tip.

Left untouched (per scope)

• The #[ApiFilter] "scheduled for removal in API Platform 5.0" [!WARNING] blocks at
  core/doctrine-filters.md (Nested Properties / Enabling a Filter for All Properties sections) —
  another agent is fixing this wording on the 4.3 branch; touching it here would conflict on
  merge-up.
• core/configuration.md and core/subresources.md — owned by another agent on this same
  workstream.

Test plan

• npx prettier@3.9.5 --check "**/*.md" --prose-wrap always passes repo-wide.
• Docs build/preview (not run locally; CI covers this).