Rewrite find-meta function to support r7rs

[VSteveHL]

• Refactored the find-meta function in analysis/identifier/meta.sls using case-lambda, adding the top-environment parameter to distinguish between r6rs and r7rs.
• Added symbol information for r7rs in analysis/identifier/meta.sls.

[ufo5260987423]

line 33: redundant

[VSteveHL]

I have renamed the R7RS symbol information in analysis/identifier/meta.sls to follow the format (scheme base). Based on my research, this naming convention is consistent with how R7RS libraries are typically introduced. Here are some references that support this approach:

• Goldfish Scheme: The README includes a section on R7RS Standard Libraries. Link
• S7 Scheme: The r7rs.scm source file. Link
• Racket-R7RS: A third-party library for Racket implementing the R7RS-small standard. Link

Additionally, I reviewed the existing symbol information in analysis/identifier/meta.sls and confirmed that this naming convention does not conflict with previously defined symbols. Given this, I believe using the (scheme base) format for R7RS symbol information is a reasonable and consistent choice.