refactor: use forked xml package for writing

[cuixq]

#1184

We would like to modify Go's implementation on self-closing tags and this PR is the first step:

• add encoding/xml to internal/thirdparty (also ignore this directory for lint)
• make Maven manifest writing to use the internal version of xml
• modify xml to not escape char data so we can call xml.EncodeToken()

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.77946% with 399 lines in your changes missing coverage. Please review.

Project coverage is 67.65%. Comparing base (9dc3afa) to head (0c6554d).

Files with missing lines	Patch %	Lines
internal/thirdparty/xml/marshal.go	77.57%	108 Missing and 51 partials ⚠️
internal/thirdparty/xml/xml.go	87.45%	82 Missing and 33 partials ⚠️
internal/thirdparty/xml/read.go	80.13%	66 Missing and 23 partials ⚠️
internal/thirdparty/xml/typeinfo.go	89.71%	17 Missing and 5 partials ⚠️
internal/resolution/manifest/maven.go	51.72%	4 Missing and 10 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1223      +/-   ##
==========================================
+ Coverage   65.22%   67.65%   +2.43%     
==========================================
  Files         170      174       +4     
  Lines       14434    16719    +2285     
==========================================
+ Hits         9415    11312    +1897     
- Misses       4501     4776     +275     
- Partials      518      631     +113     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.