Fix uninstall_extension dropping prefix-named sibling extensions

[jnasbyupgrade]

pgtle.uninstall_extension() located which extension registration functions to
drop using LIKE patterns of the forms <extname>%.control and
<extname>%.sql. Because the % immediately follows the extension name, the
patterns also matched the artifacts of any other extension whose name has
<extname> as a prefix. Uninstalling foo therefore silently dropped the
registration of foo_bar as well — no error, no warning. An extension name may
also legally contain _, which is itself a LIKE wildcard, widening the
over-match further (e.g. foo_bar also matched fooXbar). The empty-string
case is the degenerate extreme: uninstall_extension('') matched %.control
and attempted to drop every registered extension's control function.

Fix:

• The control function is named exactly <extname>.control, so match it by
  equality instead of a pattern.
• Script functions are named <extname>--<version>.sql and
  <extname>--<from>--<to>.sql. Since neither an extension name nor a version
  may contain --, that separator is a reliable boundary. Match them with an
  anchored regular expression (^<ext>--...\.sql$), regex-escaping the name
  and version so any metacharacters they contain are treated literally.

Switching the script match from LIKE to a regex also lets the two-arg
uninstall_extension(name, version) express "the version is one of the
---delimited tokens" precisely. This matches the documented behavior
("removes all update paths that use this extension version") and removes a
latent over-match where, e.g., version 1.1 also matched a 1.10 update
script via LIKE '%1.1%'.

The fix is delivered as a new 1.5.2 -> 1.5.3 upgrade script that replaces
both uninstall_extension overloads, so existing installs pick it up via
ALTER EXTENSION pg_tle UPDATE.

Behavior change: uninstall_extension('') and uninstall_extension('', '')
now report that the (empty-named) extension does not exist, and
uninstall_extension_if_exists('') returns false, instead of attempting to
drop an unrelated extension's functions. The pg_tle_functions_acl expected
output is updated accordingly.

Testing: added a focused block to pg_tle_management covering a prefix target
(with an update path), a longer-named sibling, an underscore decoy, and the
two-arg control-drop path; all survive/are removed as expected. Verified the
1.5.2 -> 1.5.3 upgrade path activates the fix on existing installs.

By submitting this pull request, I confirm that my contribution is made under
the terms of the Apache 2.0 license.

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