feat: allow reading tag variables after they are written

[DylanPiercey]

Description

Tag variables staying in the past after being written has been shown to be cumbersome, error prone, and confusing.

With that we decided to allow reading the "proposed" value after a tag variable has been written.
It is considered "proposed" because rendering logic, derivations and change handlers do not run eagerly when the assignment happens, however in the scope of the current expression you are able to read the last assigned to value of the tag variable.

<let/count=0>
<button onClick() {
  count++;
  console.log(count); // previously would be `0` on first click, now `1`
}/>

Checklist:

• I have read the CONTRIBUTING document and have signed (or will sign) the CLA.
• I have updated/added documentation affected by my changes.
• I have added tests to cover my changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: 06e46dc

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@marko/runtime-tags	Patch

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[codecov]

Codecov Report

Attention: Patch coverage is 89.06250% with 7 lines in your changes missing coverage. Please review.

Project coverage is 88.03%. Comparing base (064f068) to head (06e46dc).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ckages/runtime-tags/src/translator/util/signals.ts	87.93%	7 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2745   +/-   ##
=======================================
  Coverage   88.03%   88.03%           
=======================================
  Files         362      362           
  Lines       44419    44453   +34     
  Branches     3406     3412    +6     
=======================================
+ Hits        39103    39133   +30     
- Misses       5291     5295    +4     
  Partials       25       25           

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