<license/> in XMIR should have SPDX format, instead of raw text

[h1alexbel]

Currently, we put the whole license text inside <license/>. Instead, we should parse it like this:

<program>
  <license name="MIT">2023-2025 Yegor Bugayenko</license>
</program>

This way it would be compliant with SPDX

This message motivates this issue.

[h1alexbel]

@maxonfjvipon Assign me, please

[yegor256]

@h1alexbel I suggest we get rid of the license entirely in EO syntax, and move this info into the meta section:

+copy SPDX-FileCopyrightText 2023-2025 Yegor Bugayenko
+copy SPDX-License-Identifier MIT

# No comments.
[] > foo

Everything that goes after +spdx turns into SPDX compliant directives:

# SPDX-FileCopyrightText: 2023-2025 Yegor Bugayenko
# SPDX-License-Identifier: MIT

In other words, no more "license" that may start a .eo file.

[h1alexbel]

@yegor256 I like it. @maxonfjvipon ^ WDYT? (please assign me, if you like the idea)

[0pdd]

@h1alexbel the puzzle #3965 is still not solved.