go/runtime/host/tdx: Resize overlay image if needed

[kostko]

Fixes #6076

[netlify]

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Name	Link
🔨 Latest commit	90ff4c1
🔍 Latest deploy log	https://app.netlify.com/sites/oasisprotocol-oasis-core/deploys/67b87969ef61d400082e3775

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 27 lines in your changes missing coverage. Please review.

Project coverage is 64.86%. Comparing base (4407d4e) to head (90ff4c1).
Report is 18 commits behind head on master.

Files with missing lines	Patch %	Lines
go/runtime/host/tdx/qemu.go	0.00%	27 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6077      +/-   ##
==========================================
- Coverage   65.32%   64.86%   -0.47%     
==========================================
  Files         635      636       +1     
  Lines       64635    64641       +6     
==========================================
- Hits        42225    41929     -296     
- Misses      17513    17823     +310     
+ Partials     4897     4889       -8     

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