refactor(gnovm): rename precompiler to transpiler, move to own package

[thehowl]

Part 1 of several transpiler refactors I intend to perform.

This PR tackles one of the first pet peeves I have about the precompile tool, which is that the name is not intuitive to what it does.

Transpile is a name that not everyone likes. Ultimately, converting one source code to another is also an act of "compilation"; in fact, the TypeScript tool that converts it into JavaScript is called the "TypeScript Compiler". The distinction between transpiler and compiler is blurry; but I think it is useful to call what we have as a transpiler to outline that it is doing a "source-to-source" translation, which I don't think a name like compile or precompile could.

Additionally, this PR moves the source files for the transpiler into its own package, gnovm/pkg/transpiler.

One question is to whether the "constants" of the precompiler, like GnoRealmPkgsPrefixBefore, should deserve their own package or not.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 47.47%. Comparing base (f8e67c1) to head (c3e8ff8).

Files	Patch %	Lines
gno.land/pkg/gnoclient/client_txs.go	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1681      +/-   ##
==========================================
- Coverage   47.48%   47.47%   -0.02%     
==========================================
  Files         385      385              
  Lines       61406    61379      -27     
==========================================
- Hits        29159    29140      -19     
+ Misses      29810    29804       -6     
+ Partials     2437     2435       -2     

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