feat: Improve the matching of required versions

[nielsbasjes]

@cstamas Followup of this discussion on Slack https://the-asf.slack.com/archives/C7Q9JB404/p1773056234905829?thread_ts=1773053661.648449&cid=C7Q9JB404

When people write in (for example) the maven-invoker-plugin something like invoker.toolchain.jdk.version = 11 it is implemented as an exact match on the mentioned version specified in the toolchains.xml .
Historically people would write this config manually and then the exact version 11 works as expected.

With the automatic generation of the toolchains.xml more places will contain the full version of the JDK like <version>11.0.29</version> instead of the more simple <version>11</version>.

The effect of people using these automatically generated toolchains.xml files is that now things still work as designed, but not as expected.

This is a quick implementation of my proposal to simply treat the requirement of a single number X as "the major version must be X".
I have also included the same for a "major.minor" requirement to accept all patch versions under that also.

This means a change from a mismatch to a match in cases like this:

matcher = RequirementMatcherFactory.createVersionMatcher("1.5.2");
matcher.matches("1.5");

I'm unsure if this change is "too breaking" to be implemented.

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[cstamas]

Take a peek at "counter pr" #11786

[slawekjaranowski]

We can move pattern compile to static filed

[gnodet]

Claude Code on behalf of Guillaume Nodet

Nice idea to make toolchain version matching more lenient for the auto-generated toolchains.xml use case. Two issues I spotted:

1. Regex bug: The major.minor pattern only allows a single-digit major version, so "21.3" would not match. Needs [0-9]+ for the major part too.
2. Pattern precompilation: As @slawekjaranowski already noted, the patterns should be compiled once into static fields.
3. Missing test coverage: No tests for multi-digit major versions (e.g., requirement "21" against version "21.0.2", or "21.3" against "21.3.1").

[gnodet]

Bug: the major version part is [0-9] (single digit only), so a requirement like "21.3" would silently fall through to the default path and be treated as an exact match. It should be [0-9]+ to mirror the first pattern.

Suggested change

	if (Pattern.matches("^[0-9]\\.[0-9]+$", requirement)) {
	if (Pattern.matches("^[0-9]+\\.[0-9]+$", requirement)) {

Also, as @slawekjaranowski mentioned, both patterns should be pre-compiled into private static final Pattern fields to avoid recompilation on every call.

[gnodet]

Consider adding tests for multi-digit major versions to catch the regex bug above, e.g.:

matcher = RequirementMatcherFactory.createVersionMatcher("21.0.2");
assertTrue(matcher.matches("21"));     // major-only
assertTrue(matcher.matches("21.0"));   // major.minor
assertFalse(matcher.matches("21.1")); // wrong minor
assertFalse(matcher.matches("2"));     // wrong major