feat(maven): improve PreFetch for Maven

[cuixq]

We disabled PreFetch in #1466 and this caused the resolution performance worse for deps.dev client.

To enable PreFetch, we need to avoid unnecessary requests of maven-metadata.xml files which is a result of calling MatchingVersions and Versions.

This PR improves the logic in PreFetch so that MatchingVersions is only called for non-soft Maven requirements and Versions is called for ecosystems other than Maven.

It used to take about 1m to resove pom.xml without PreFetch enabled and now it takes less than 20 seconds.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.61538% with 4 lines in your changes missing coverage. Please review.

Project coverage is 66.94%. Comparing base (7acec29) to head (c594fbb).

Files with missing lines	Patch %	Lines
internal/resolution/client/client.go	84.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1485      +/-   ##
==========================================
+ Coverage   66.84%   66.94%   +0.09%     
==========================================
  Files         198      198              
  Lines       18650    18660      +10     
==========================================
+ Hits        12467    12492      +25     
+ Misses       5498     5486      -12     
+ Partials      685      682       -3     

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[michaelkedar]

Nice