General: Fix wp_get_tooltip_helper() treating button markup as sprintf() format string.

[parthjogi-nyusoft]

Fixes #65914

wp_get_tooltip_helper() concatenated caller-supplied button markup directly
into a sprintf() format string. Any % in that markup (e.g. a percent-encoded
URL, or a meta box ID like sale_100%_off) was parsed as a conversion
specification, causing either a fatal ValueError or silently corrupted output.

This patch passes the button markup to sprintf() as a plain argument instead
of concatenating it into the format string. The default core-generated
button's label/icon/popovertarget placeholders are now filled via
str_replace() on internal tokens before that point, so default-button
behavior is unchanged.

Added 5 tests to tests/phpunit/tests/general/wpGetTooltip.php covering the
exact repro cases from the ticket plus a regression check for the default
button. Full test file passes locally: 16 tests, 43 assertions.

Trac ticket: https://core.trac.wordpress.org/ticket/65914

Use of AI Tools

AI assistance: Yes
Tool(s): Claude (Anthropic)
Used for: Diagnosis of the root cause, implementation of the fix, and the
regression test suite. I reviewed the code, applied it in my local
wordpress-develop environment, and ran the full test suite
(16 tests, 43 assertions, all passing) before submitting.

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